A dog can hear sounds in the range from 15
to 50,000 Hz.
What wavelength corresponds to the lower
cut-off point of the sounds at 20◦C where the
sound speed is 344 m/s?
Answer in units of m.

v = fλ links the velocity, frequency, and wavelength of a wave and is used to compute one of these parameters if the other two are known.

The wavelength formula shows the wavelength in metres. The v represents wave velocity and is measured in metres per second (mps). In addition, the letter "f" stands for frequency, which is expressed in hertz (Hz).

The term wavelength implies that it measures length. Its measurements are often expressed in length measurements or metric units. In other words, wavelengths can be expressed in their SI units, metres.

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Momentum is not always conserved in real-life situations because external forces can act on a system and change its momentum.

For example, when two cars collide, friction and air resistance can cause the momentum of the system to change. Similarly, when a ball is thrown in the air, gravity and air resistance act on it and cause its momentum to change. Other factors such as deformation, energy loss, and imperfect collisions can also cause momentum to be lost or gained. Therefore, while momentum is a useful concept in physics, it is important to consider the impact of external factors when analyzing real-world situations.

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The tension in the string of a 1.85 kg package held by a light vertical string will depend on the acceleration of the elevator. When the elevator accelerates, the force of acceleration on the package will be equal and opposite to the tension in the string, causing the tension to increase.

The equation for tension in a string is:

Tension = Mass x Acceleration

Therefore, in this case, the tension in the string is equal to 1.85 kg x Acceleration.

If we assume that the acceleration of the elevator is a constant rate, then the tension in the string can be calculated by multiplying the mass of the package by the acceleration of the elevator.

To sum up, the tension in the string of a 1.85 kg package held by a light vertical string will depend on the acceleration of the elevator. If the acceleration of the elevator is a constant rate, then the tension in the string can be calculated by multiplying the mass of the package by the acceleration of the elevator.

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From the sketch, we can deduce that the two charges q1 and q2 are of opposite signs, as field lines start at the positive charge q1 and end at the negative charge q2. The field lines also indicate that the magnitude of the electric field produced by q1 is larger than that of q2.

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The minimum thickness of the film for constructive interference of reflected light would be t = 3*600/(2*1.4) = 850 nm.

The minimum thickness of a film required for constructive interference of reflected light can be calculated using the formula t = m*λ/(2*n),

where t is the minimum thickness of the film, m is the order of interference, λ is the wavelength of the light, and n is the index of refraction of the film.

For example, if the order of interference is 3, the wavelength of the light is 600 nm, and the index of refraction is 1.4,

the minimum thickness of the film for constructive interference of reflected light would be t = 3*600/(2*1.4) = 850 nm.

Constructive interference of reflected light occurs when the phase difference between the two waves is equal to an integral multiple of 2π.

This can be determined using the formula Δφ = (2π*m)/(λ*n), where Δφ is the phase difference, m is the order of interference, λ is the wavelength of the light, and n is the index of refraction of the film.

To achieve constructive interference, the minimum thickness of the film can be determined by ensuring that the phase difference is equal to an integral multiple of 2π.

The minimum thickness of a film required for constructive interference of reflected light can be calculated using the formula t = m*λ/(2*n),

where t is the minimum thickness of the film, m is the order of interference, λ is the wavelength of the light, and n is the index of refraction of the film.

Constructive interference can be achieved by ensuring that the phase difference between the two waves is equal to an integral multiple of 2π.

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The time it takes the object to fall through the change in speed using the impulse-momentum theorem is 0.62 seconds.

The impulse-momentum theorem states that the change in momentum of an object is equal to the impulse exerted on it.

To calculate the time it takes the object to increase it speed using the  impulse-momentum theorem, we use the formula below.

Formula:

Recall that F/m = acceleration. Therefore,

Where:

From the question,

Given:

Substitute these values into equation 1 and solve for t

Hence, the time it takes the object to fall is 0.62 seconds.

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The formula for calculating capacitance is as follows:

C = Q/V

Where,

C = capacitance (Farads)

Q = charge (Coulombs)

V = voltage (Volts)

As given,

Q = 27.0 μC

V = 9.00 V

Substituting the given values in the above equation

C = 27.0 μC/9.00 V = 3.00 μF

Therefore, the value of capacitance is 3.00 μF.

The formula for calculating charge stored is as follows:

Q = CV

Where,

Q = charge (Coulombs)

C = capacitance (Farads)

V = voltage (Volts)

As given,

C = 3.00 μF

V = 12.0 V

Substituting the given values in the above equation,

Q = (3.00 × 10⁻⁶ F) × 12.0 V = 36.0 μC

Therefore, the charge stored is 36.0 μC.

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Each aircraft must be moving at a speed of 85.75 km/hr towards each other to hear a pitch that is 2 times the emitted frequency.

What is frequency ?

Frequency is a physical quantity that describes the number of occurrences of a repeating event per unit of time. It is often measured in Hertz (Hz), which represents the number of cycles or vibrations per second.

In the context of waves, such as sound waves or electromagnetic waves, frequency refers to the number of complete cycles of the wave that occur in one second. A high frequency wave has more cycles per second than a low frequency wave.

Frequency is also an important concept in physics, particularly in the study of oscillations and waves. It is used to describe the behavior of systems that oscillate or vibrate, such as a simple pendulum or a guitar string. In these cases, the frequency of the oscillation is related to the natural frequency of the system, which is determined by its mass, stiffness, and other properties.

When two aircraft are moving towards each other, the sound waves from each aircraft are compressed, leading to a higher pitch than the emitted frequency. The pitch heard by the pilots of the aircraft can be calculated using the following formula:

Pitch heard = Emitted frequency * (Speed of sound + Speed of observer) / (Speed of sound - Speed of source)

Since the two aircraft are flying towards each other at the same speed, we can assume that the speed of one aircraft is x km/hr, and the speed of the other aircraft is also x km/hr. Therefore, the relative speed between the two aircraft is 2x km/hr.

Substituting the values given in the formula, we get:

2 * Emitted frequency = Emitted frequency * (343 + 2x) / (343 - x)

Simplifying this equation, we get:

686 - 2x = 343 + 2x

4x = 343

x = 85.75 km/hr

Therefore, each aircraft must be moving at a speed of 85.75 km/hr towards each other to hear a pitch that is 2 times the emitted frequency.

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The given statement " A series circuit is a current divider and a parallel circuit is a voltage divider circuit " is True

In a series circuit, the electric current is the same through each component, and the total current is equal to the sum of the currents through each component. Therefore, the current is divided among the components.

In a parallel circuit, the potential voltage across each component is the same, and the total voltage is equal to the sum of the voltages across each component. Therefore, the voltage is divided among the components.

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The television commercial loudness increases by 10 decibels.

The decibel (dB) scale is a logarithmic measure of sound intensity. The intensity of a sound is measured in watts per square meter and the decibel scale is a way to express the relative loudness of a sound, compared to a reference level.

A 10 dB increase in intensity is a 10-fold increase in sound power. This means that a sound with an intensity of 10 watts per square meter is 10 times louder than a sound with an intensity of 1 watt per square meter.

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The first-order maximum for 450-nm wavelength blue light falling on double slits separated by 0.0500 mm is approximately 6.2°.

The angle of the first-order maximum refers to the angle at which the brightest interference pattern appears on a screen placed behind two closely spaced slits when illuminated with the blue light of 450-nm wavelength.

The angle is determined by the equation:

theta_m = (m*lambda)/d

where m is the order, lambda is the wavelength, and d is the slit separation.
theta_m = (1*450E-9 m)/0.0500 mm
theta_m = 6.2°

Thus, the first-order maximum for double slits of 0.0500 mm at 450 nm λ blue light is around 6.2°.

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For a spherical capacitor with a capacitance of 125 and a vacuum between its conducting shells, the outer radius of the inner shell is around 5.60 cm.

The capacitance of a spherical capacitor is given by:

C = 4πε₀[(r₁r₂)/(r₂-r₁)]

where C is the capacitance, ε₀ is the electric constant (8.85 x [tex]10^{-12}[/tex] F/m), r₁ is the radius of the inner shell, and r₂ is the radius of the outer shell.

In this case, we know that the capacitance C = 125 pF (picoFarads), r₂ = 9.00 cm, and we want to find r₁.

We can rearrange the equation to solve for r₁:

r₁ = (C × r₂)/(4πε₀ + C)

Substituting the values:

r₁ = (125 x [tex]10^{-12}[/tex] F × 0.09 m) / (4π × 8.85 x [tex]10^{-12}[/tex] F/m + 125 x [tex]10^{-12}[/tex] F)

r₁ ≈ 5.60 cm

Therefore, the outer radius of the inner shell is approximately 5.60 cm.

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a..... 1.04 x 10⁻⁴ Vi

b.... 9500 V

A) Determine the capacitance (to the nearest 10 μF).

First, we should identify the formula that we will use to solve the problem.

The formula that relates to capacitance is:

C = 2E / V². Where C is the capacitance in farads, E is the energy stored in joules, and V is the voltage across the capacitor in volts.

Converting the energy to joules, we have: E = 250J.

Now we know that the voltage needs to drop to half of its initial value in 10 ms. We can use the following formula to calculate the capacitance: C = R x t / ln(Vi / Vf) where R is the resistance in ohms, t is the time in seconds, Vi is the initial voltage, and Vf is the final voltage, which is half of the initial voltage.

B) Plugging in the given values, we get:

C = 48 x 0.01 / ln(Vi / (Vi / 2))Simplifying and solving for capacitance, we get:

C = 1.04 x 10⁻⁴ ViNow we can use the energy formula to solve for Vi:Vi = √(2E / C)

Plugging in the given values, we get:Vi = √(2 x 250 / 1.04 x 10⁻⁴)Simplifying and solving for Vi, we get:Vi = 9469 V

Therefore, the capacitance that meets these specifications is 100 μF and the initial capacitor voltage that meets these specifications is 9500 V, to the nearest 100 V.

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Option D: 2 m/s is the average velocity of the water flowing through a pipe with a cross-sectional area of 0.002 m2 at a mass flow rate of 4 kg/s.

According to the question:

cross-sectional area of the pipe = 0.002m²

Mass flowrate = 4 kg/s

Density of water = 1000 kg/m³

We are asked to find, average velocity =?

Average velocity is the net or total displacement covered by a body in a given time. The mass flow rate divided by the pipe's cross-sectional area and density ratio is the formula for calculating a fluid's average velocity.

As a result, the water's average flow rate through the pipe is provided by:

v = m / (ρ × A)

where, v is the average velocity, m is the mass flow rate, ρ is the density of water, and A is the cross-sectional area of the pipe. Substituting the values in the above equation we get:

v = 4 / (1000 × 0.002)

v = 2m/s

Therefore, the average velocity of water flowing through a pipe of cross-sectional area of 0.002m² is 2m/s.

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Correct question is:

Water flows through a pipe with a cross-sectional area of 0.002 m2 at a mass flow rate of 4 kg/s. The density of water is 1 000 kg/m3. Determine its average velocity. Multiple choice question.

20 m/s

200 m/s

0.02 m/s

2 m/s

0.2 m/s

The period of a mass-spring oscillating system undergoing SHM with a period t, when the amplitude is doubled, is still t.

The period of a mass-spring oscillating system undergoing simple harmonic motion (SHM) is determined by the spring constant and mass of the system.

When the amplitude of the system is doubled, the period of the system remains the same, regardless of the amplitude. This means that the period of a mass-spring oscillating system undergoing SHM with a period t, when the amplitude is doubled, is still t.
To understand why the period remains the same, consider the equation for simple harmonic motion:

x(t) = A cos (2πft).

This equation describes the displacement of an object over time and is based on the principle that any system undergoing SHM oscillates about a fixed point at a constant frequency.

The frequency of the system is inversely proportional to the period, and is determined by the spring constant and mass of the system.

Increasing the amplitude of the system does not affect the frequency or period of the oscillations.

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The sound level for this noise is approximately 50 decibels.

Sound level is a logarithmic measure of the ratio between the sound pressure level of a particular sound wave and a reference level. The reference level is typically set at the threshold of human hearing, which corresponds to an intensity of 10^-12 W/m^2. The sound level (measured in decibels, dB) of a sound wave is given by,

L = 10 log10(I/I0)

where I is the intensity of the sound wave and I0 is the reference intensity, which is typically set at 10^-12 W/m^2.

So, for an intensity of 10^-7 W/m^2 in a typical classroom, we can calculate the sound level as,

L = 10 log10(I/I0) = 10 log10(10^-7/10^-12) = 10 log10(10^5) = 50 dB

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The magnitude of the torque on the current loop is calculated using the formula τ=BIA sinθ, where B is the magnitude of the magnetic field, I is the current, A is the area of the loop, and θ is the angle between the magnetic field and the loop's plane. In this case, the magnitude of the torque is τ = (1.2 T)(0.5 A)(5 cm x 5 cm)sin(30°) = 7.5 x 10-3 Nm.

The torque is the rotational force that causes the loop to rotate. This is due to the fact that a force is exerted on the loop by the magnetic field when there is a current running through it. This force generates a torque on the loop, which will cause it to rotate until the angle between the plane of the loop and the magnetic field is 0°.

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The force generated per unit field strength on a 20.0 cm wide section of the loop with a current of 5.5 A is: 0.001 newtons per tesla

The force generated per unit field strength on a 20.0 cm wide section of the loop with a current of 5.5 A is given by the formula F = (μI) / 2πr,

where μ is the permeability of free space, (4π x 10-7 N/A²)

I is current, and r is the radius of the loop.

In this case, the force is (4π x 10-7 x 5.5) / (2π x 0.1) = 0.001 N/T.

In other words, the force generated per unit field strength on a 20.0 cm wide section of the loop with a current of 5.5 A is 0.001 newtons per tesla.

The formula for the force generated per unit field strength on a loop is derived from the fact that the force is a result of the magnetic field generated by the current flowing in the loop.

The magnitude of the magnetic field generated is proportional to the current and inversely proportional to the radius of the loop. Since the force is a product of the current and the magnetic field, it is proportional to the square of the current and inversely proportional to the square of the radius of the loop.

In summary, the force generated per unit field strength on a 20.0 cm wide section of the loop with a current of 5.5 A is 0.001 newtons per tesla, given by the formula F = (μI) / 2πr, where μ is the permeability of free space (4π x 10-7 N/A²), I is current, and r is the radius of the loop.

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The process described in the question is known as scenario planning. It is a strategic planning method that involves generating multiple plausible scenarios of future conditions and analyzing the potential impact of each scenario on an organization or a system.

Scenario planning is a useful tool for decision-making, risk management, and identifying opportunities in an uncertain or rapidly changing environment.

By developing a range of scenarios, decision-makers can anticipate potential challenges and opportunities and develop strategies to respond effectively to each situation.

This approach allows organizations to be better prepared and more resilient in the face of future uncertainties. Scenario planning can be applied to various fields, including business, economics, environmental planning, and public policy.

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The skydiver covered a distance of approximately 94.9 meters before opening his parachute between t1 and t2, assuming no air resistance or friction.

v = final velocity = v2 = 27 m/s

u = initial velocity = v1 = 11 m/s

a = acceleration = g = 9.8 m/[tex]s^2[/tex]

s = (v² - u²) / 2a

s = (27² - 11²) / (2 x 9.8) = 94.9 meters

Resistance measures an item's potential to impede the drift of electrical present-day through it. it's far measured in ohms (Ω). Resistance is decided by way of the bodily residences of an item, along with its dimensions, material, and temperature. while electric-powered present-day flows thru a conductor, it encounters resistance that slows down its float. This resistance is as a result of the collisions among electrons and the atoms inside the conductor.

Resistance can be laid low with changes inside the bodily properties of the conductor, such as duration, cross-sectional region, or temperature. an extended or narrower conductor may have higher resistance, even as a much broader conductor could have decreased resistance. understanding resistance is critical for designing and working electrical circuits. with the aid of controlling the resistance of a circuit, engineers can make sure that the appropriate amount of current flows to electricity the devices linked to it.

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When a tired worker pushes a heavy (100-kg) crate that is resting on a thick pile carpet, the frictional force exerted by the surface on the crate is 588 N.

When a tired worker pushes a heavy (100-kg) crate that is resting on a thick pile carpet, the frictional force exerted by the surface can be calculated as follows:

The weight of the crate = m × g = 100 kg × 9.8 m/s² = 980 N

Force applied by the worker = F = 600 N

The force of friction acting on the crate is given by the following formula:

Ff = μF

Where, μ is the coefficient of friction, F is the normal force acting on the crate.

Notes: The normal force is equal and opposite to the weight of the crate. i.e., N = 980 N1. The frictional force exerted by the surface on the crate is the static frictional force initially. Hence, we use the coefficient of static friction for our calculation.

2. If the force applied by the worker is not enough to overcome the static frictional force, then the crate will not move and the frictional force will remain static friction.

3. Once the crate starts moving, the static friction will convert to kinetic friction. Hence, we will use the coefficient of kinetic friction if the force applied by the worker is greater than the force of static friction. Initially, the force applied by the worker is less than the force of static friction, hence the frictional force exerted on the crate will be the static frictional force.

Frictional force = Ff = μN

The normal force acting on the crate = Weight of the crate = 980 N

Frictional force =

Ff = μN

= 0.6 × 980 N

= 588 N

Therefore, the frictional force exerted by the surface on the crate is 588 N.

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The projectile will be moving at a speed of 57.21 m/s when it reaches the top of its trajectory.

When a projectile is fired at a speed of 138 and an upward angle of 65 degrees, the speed at the top of the trajectory can be calculated. To solve this problem, you need to understand some basic physics concepts. Here's how you can solve this problem:
1. First, identify the given values and write them down:
Initial velocity (u) = 138 m/s
Angle of projection (θ) = 65 degrees
Acceleration due to gravity (g) = 9.81 m/s²
2. Now, break down the initial velocity into its horizontal and vertical components:
Initial velocity in the horizontal direction = u cos θ
Initial velocity in the vertical direction = u sin θ
3. Use the equation of motion to calculate the time taken by the projectile to reach the top of its trajectory:
u sin θ = gt/2
t = 2u sin θ/g
4. Use the time obtained in step 3 to calculate the velocity at the top of the trajectory:
v = u cos θ
Where,
v = final velocity
u = initial velocity
θ = angle of projection
5. Substitute the given values in the equation to get the final answer:
v = u cos θ
v = 138 cos 65
v = 57.21 m/s
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The true statements about the radial (centripetal) acceleration and the tangential acceleration at the end of the blade are: the radial acceleration is non-zero the tangential acceleration is zero

The radial acceleration is non-zero and the tangential acceleration is zero. This is because, the radial acceleration is determined by the formula, ar = (v²)/r

where ar is the radial acceleration, v is the velocity and r is the radius. Thus, since the propeller blade is spinning at a constant rate, the velocity v is constant.

Therefore, the radial acceleration is constant and non-zero.

The tangential acceleration, on the other hand, is given by at = rα

where at is the tangential acceleration and α is the angular acceleration. Since the blade is spinning at a constant rate, the angular acceleration is zero. Therefore, the tangential acceleration is zero.

So, the correct option is the radial acceleration is non-zero and the tangential acceleration is zero.

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The force would be 6 Newtons for a distance of 30 metres.

A force is defined as any influence that results in a change in an object. Distance is the amount of distance that an object moves over time. A force is applied to an item, and the more force is applied, the farther the thing will move.

Action-at-a-distance forces are those that develop even when the two interacting objects are not in close proximity to one another but are nevertheless able to push or pull against one another despite this physical gap.

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When a resistor and a capacitor are connected in series across an ideal battery, the voltage across the capacitor is zero at the moment contact is made with the battery.

The correct option is c.

An ideal battery is a voltage source that delivers a constant voltage regardless of the load resistance or current drawn from it.

An ideal battery can maintain a steady voltage regardless of the amount of current being drawn from it.

In real-life batteries, there is always some internal resistance, which causes the voltage to drop as the current increases.

A resistor is an electrical component that opposes or limits the flow of electrical current. It has two terminals and can be made of various materials like carbon, metal, and ceramic. It is used in various applications, including voltage dividers, current limiting, and biasing.

A capacitor is an electronic component that stores energy in an electric field between two charged conductors. It has two terminals and is made of two conducting plates separated by an insulating material called a dielectric.

Capacitors are used in various applications, including energy storage, timing circuits, and power conditioning.

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A brick is falling from the roof of three story building then free-body diagram would show only one force vector, which is the force of gravity acting on the brick.

A free-body diagram is used to graphically represent the forces acting on an object. It shows all of the forces acting on an object and can be used to analyze the motion of an object.

A free-body diagram for a falling brick would include two force vectors: Gravity or Weight.

So, in this scenario, the free-body diagram would show only one force vector, which is the force of gravity acting on the brick.

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The value of  uncharged capacitor in series with a 10.0-microfarad capacitor, given that each capacitor has a voltage of 3.00 volts, can be calculated using the formula for equivalent capacitance in series and  formula for charge on a capacitor. The value of c is approximately 4.00 microfarads.

To determine the value of c, which is [tex]1/Ceq = 1/C1 + 1/C2[/tex] . Initially, the 10.0-microfarad capacitor has a charge of [tex]Q = CV = (10.0 * 10^{-6 }F) * 12.0 V = 1.20 * 10^{-4} C[/tex].

When it is connected in series with uncharged capacitor with capacitance c,  charge is shared between the two capacitors. The charge on  10.0-microfarad capacitor is also equal to the charge on  uncharged capacitor, which is given by [tex]Q = (3.00 V) * C[/tex] .

Equating the two expressions for Q and solving for c, we get [tex]C = Q/3.00[/tex] [tex]V = (1.20 * 10^{-4 C}) / (3.00 V) = 4.00 * 10^{-5 F}[/tex]. Therefore,  value of c is approximately 4.00 microfarads.

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In an n-type piece of silicon, the electric field causes the electrons to accelerate due to the attractive force between the negatively charged electrons and the positively charged electric field. This acceleration causes the electrons to reach a velocity of V = E/μ, where E is the electric field (0.1V/m) and μ is the mobility of electrons in silicon (1350 cm2/V⋅s). Therefore, the velocity of electrons in this material would be equal to 0.1V/m/1350cm2/V⋅s = 0.0741 cm/s.

The holes, on the other hand, experience a repulsive force due to the positive electric field. This causes the holes to decelerate, with a velocity of V = -E/μ. Therefore, the velocity of holes in this material would be equal to -0.1V/m/1350cm2/V⋅s = -0.0741 cm/s.

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The formula for the impulse exerted on the ball from the instant it is dropped to an arbitrary time later is:

Impulse = (Final momentum - Initial momentum)

Impulse is a vector quantity having both magnitude and direction, whereas momentum is a vector quantity, but the impulse is not equal to momentum. The impulse is the change in momentum.

If a ball of mass m is dropped from rest, then its initial momentum is zero.

The final momentum of the ball after falling for time t is:

Final momentum = mv

Where v is the velocity of the ball after falling for time t.

Therefore, the impulse exerted on the ball from the instant it is dropped to an arbitrary time later is:

Impulse = (mv - 0) = mv

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Answer:

Approximately [tex]31.3\; {\rm kg}[/tex]. (Assuming the friction between the skateboard and the ground is negligible.)

Explanation:

The momentum [tex]p[/tex] of an object of [tex]m[/tex] and velocity [tex]v[/tex] is:

[tex]p = m\, v[/tex].

When the boy tossed the jug of water, the change in the momentum of the jug would be:

[tex]\Delta p(\text{jug}) = m(\text{jug}) \, (v(\text{jug}) - u(\text{jug}))[/tex], where:

Hence:

[tex]\begin{aligned}\Delta p(\text{jug}) &= m(\text{jug}) \, (v(\text{jug}) - u(\text{jug})) \\ &= (8.0)\, (2.7 - 0)\; {\rm kg\cdot m\cdot s^{-1}} \\ &= 21.6\; {\rm kg\cdot m\cdot s^{-1}}\end{aligned}[/tex].

Similarly, the change in the momentum of the skateboard would be:

[tex]\Delta p(\text{board}) = m(\text{board}) \, (v(\text{board}) - u(\text{board}))[/tex], where:

Note that the velocity of the board [tex]v(\text{board})\![/tex] after the toss is opposite to that of the jug. The sign of [tex]v(\text{board})[/tex] would be opposite to that of [tex]v(\text{jug})[/tex]. Since [tex]v(\text{jug})\![/tex] is positive, the value of [tex]v(\text{board})\!\![/tex] should be negative.

[tex]\begin{aligned}\Delta p(\text{board}) &= m(\text{board}) \, (v(\text{board}) - u(\text{board})) \\ &= (1.9)\, ((-0.65)- 0)\; {\rm kg\cdot m\cdot s^{-1}} \\ &= (-1.235)\; {\rm kg\cdot m\cdot s^{-1}}\end{aligned}[/tex].

Let [tex]m(\text{boy})[/tex] denote the mass of the boy. The velocity of the boy was initially [tex]u(\text{boy}) = 0\; {\rm m\cdot s^{-1}}[/tex] and would become [tex]v(\text{boy}) =(-0.65)\; {\rm m\cdot s^{-1}}[/tex] after the toss. The change in the velocity of the boy would be:

[tex]\Delta p(\text{boy}) = m(\text{boy}) \, (v(\text{boy}) - u(\text{boy}))[/tex].

Under the assumptions, the total changes in the momentum of this system (the boy, the skateboard, and the jug) should be [tex]0[/tex]. Thus:

[tex]\Delta p(\text{boy}) + \Delta p(\text{boy}) + \Delta p(\text{jug}) = 0[/tex].

Rearrange and solve for the mass of the boy:

[tex]\Delta p(\text{boy}) = -\Delta p(\text{jug}) - \Delta p(\text{board})[/tex].

[tex]\begin{aligned} m(\text{boy}) &= \frac{-\Delta p(\text{jug}) - \Delta p(\text{board})}{v(\text{boy}) - u(\text{boy})} \\ &= \frac{-(21.6) - (-1.235)}{(-0.65) - 0}\; {\rm kg} \\ &\approx 31.3\; {\rm kg}\end{aligned}[/tex].