are aliens real in 2020

Given that,

At 3.00 m from a source that is emitting sound uniformly in all directions, the sound level is 60.0 dB.

To find,

The distance from the source would the sound level be one-fourth the sound level at 3.00 m.

Solution,

The intensity from a source is inversely proportional to the distance.

Let I₁ = 60 dB, r₁ = 3 m, I₂ = 60/4 = 15 dB, r₂ =?

Using relation :

[tex]\dfrac{I_1}{I_2}=\dfrac{r_2^2}{r_1^2}\\\\r_2^2=\dfrac{I_1r_1^2}{I_2}\\\\r_2^2=\dfrac{60\times (3)^2}{15}\\\\r_2=6\ m[/tex]

So, at a distance of 6 m the sound level will be one fourth of the sound level at 3 m.

Answer:

a = 0.16 [m/s²]

Explanation:

To solve this problem we must use the following equation of kinematics.

[tex]v_{f}=v_{o}+a*t\\[/tex]

where:

Vf = final velocity = 3.2 [m/s]

Vo = initial velocity = 1.1 [m/s]

t = time = 13 [s]

a = acceleration [m/s²]

Now replacing:

[tex]3.2=1.1+a*13\\2.1=13*a\\a=0.16[m/s^{2} ][/tex]

Answer:

a) [tex]F_{x} = 58.2 N[/tex]

[tex] F_{y} = 48.9 N [/tex]

b) a = 1.5 m/s²

Explanation:

a) The horizontal and vertical components of Emily's force can be found knowing the angle and the exerted force.

Since the handle is inclined at 40.0° below the horizontal we have:

[tex] F_{x} = |F|*cos(\theta) = 76.0 N*cos(40) = 58.2 N [/tex]

[tex] F_{y} = |F|*sin(\theta) = 76.0 N*sin(40) = 48.9 N [/tex]

b) The acceleration of the car can be calculated as follows:

[tex] F_{x} = ma [/tex]        

We used the horizontal component of the force because the cart is moving in that direction.

[tex] a = \frac{F_{x}}{m} = \frac{58.2 N}{38.8 kg} = 1.5 m/s^{2} [/tex]

Hence, the acceleration of the car is 1.5 m/s².    

I hope it helps you!

Given that,

Mass of student 1, m₁ = 90 kg

Mass of student 2, m₂ = 60 kg

Speed of student 1, v₁ = 5 m/s

To find,

The velocity of the other student.

Solution,

Using the conservation of momentum to find the velocity of the other student. Let it is v₂.

[tex]m_1v_1=m_2v_2\\\\v_2=\dfrac{m_1v_1}{m_2}\\\\v_2=\dfrac{90\times 5}{60}\\\\=7.5\ m/s[/tex]

So, the velocity of the other student is 7.5 m/s.

Answer: 5.91kw

Explanation:

given data:

power = 65kw

voltage stepped up = 120v t0 1200

R 0.100

Solution:

when the it is stepped to 120v

[tex]P = VI \\65000/ 120I\\ I = 541.7A\\[/tex]

power loss

[tex](I^{2} )R*2\\= (541.7^{2})0.100*2\\= 58536.2w[/tex]

when it is stepped to 1200v

[tex]\frac{65000}{1200} \\ I = 54.17A\[/tex]

[tex](I^{2} )R*2\\= (54.17^{2})0.100*2\\= 586.9w[/tex]

total power saved

[tex]= 65kw - 58.5kw - 0.59kw\\= 5.91kw[/tex]

Answer:

I think the answer is  

a "cookbook" recipe for performing scientific investigations

Explanation:

Answer:

hiiiiiiiiiiiii baby.........

Answer:

The skier will be moving at 13.31 m/s.

Explanation:

To calculate the velocity of the skier we need to find the acceleration, as follows:

[tex] \Sigma F = ma [/tex]

[tex] F_{r} - F_{f} = ma [/tex]

Where:

[tex] F_{r}[/tex]: is the force due to the rope = 365 N

[tex] F_{f}[/tex]: is the combined average frictional force = 190 N

m: is the mass = 75.0 kg

[tex] a = \frac{365 N - 190 N}{75.0 kg} = 2.33 m/s^{2} [/tex]

Now, we can calculate the velocity of the skier by using the following kinematic equation:

[tex] v_{f}^{2} = v_{0}^{2} + 2ad [/tex]

Where:

[tex] v_{f}[/tex]: is the final velocity =?

[tex] v_{0}[/tex]: is the initial velocity = 0 (the skier is initially at rest)

d: is the distance = 38.0 m

[tex] v_{f} = \sqrt{2*2.33 m/s^{2}*38.0 m} = 13.31 m/s [/tex]

Therefore, the skier will be moving at 13.31 m/s.

I hope it helps you!                                                                                  

Answer:

The heat absorbed in each cycle is 9,234.286 J

Explanation:

Given;

power output, P = 5 kW = 5,000 W

efficiency of the engine, e = 30 % = 0.3

thermal heat expelled, [tex]Q_c[/tex] = 6464 J

let the heat absorbed = [tex]Q_h[/tex]

The efficiency of the engine is given as;

[tex]e = \frac{W}{Q_h} = \frac{Q_h-Q_c}{Q_h} = \frac{Q_h}{Q_h} - \frac{Q_c}{Q_h} = 1-\frac{Q_c}{Q_h}\\\\e = 1-\frac{Q_c}{Q_h}\\\\0.3 = 1-\frac{Q_c}{Q_h}\\\\\frac{Q_c}{Q_h} = 1-0.3\\\\\frac{Q_c}{Q_h} = 0.7\\\\Q_h = \frac{Q_c}{0.7} \\\\Q_h = \frac{6464}{0.7} = 9,234.286 \ J.[/tex]

Therefore, the heat absorbed in each cycle is 9,234.286 J.

Answer:

Light travels as a wave. But unlike sound waves or water waves, it does not need any matter or material to carry its energy along. This means that light can travel through a vacuum—a completely airless space. It speeds through the vacuum of space at 186,400 miles (300,000 km) per second.

Explanation:

Hope this helps :))

Answer:

The correct answer is 4R1

Explanation:

According to the given scenario ,the radius of the tightest curve on the same road without skidding is as follows:

As we know that

Centeripetal Acceleration is

= v^2 ÷ r

In the case when velocity becomes 2 times so the r would be 4 times

So, the radius of the  tightest curve on the same road without skidding is 4R1

Answer:

As tectonic plates slowly move away from each other, heat from the mantle's convection currents makes the crust more plastic and less dense.

Explanation:

Answer: The main cause of sea floor spreading are the directions and force of the moving tectonic plates.

Explanation:

An electric current causes the magnetic field around the wire. The correct answer is A.

The magnetic field around a wire is caused by the flow of electric current through the wire. When an electric current passes through a wire, it generates a magnetic field that forms circular lines of magnetic flux around the wire. This phenomenon is described by Ampere's law, which states that a magnetic field is produced by an electric current and its strength is directly proportional to the magnitude of the current.

The relationship between the electric current and the magnetic field can be understood using the right-hand rule. If you wrap your right hand around the wire with your thumb pointing in the direction of the current, the curled fingers indicate the direction of the magnetic field lines.

Therefore, an electric field is generated by an electric charge, not by an electric current. While an electric field can exist around a wire if there is a potential difference (voltage) applied across it, it is the flow of electric current that primarily generates the magnetic field.

To learn more about the electric field click:

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#SPJ1

Answer: All UV can have harmful effects on biological matter (such as causing cancers) with the highest energies causing the most damage.

Explanation:

Answer:

Question 4 is actually Acceleration

Answer:

same for all objects

Explanation:

earth pulls every object by same force of gravity

a = v² / R = (2 m/s)² / (0.1 m) = 40 m/s²

Answer:

[tex]v_{PB} = 130\ km/h[/tex]

Explanation:

Since, Alex is at rest. Therefore, the speed measured by him will be the absolute speed of car P. Therefore, taking easterly direction as positive:

[tex]Absolute\ Velocity\ of\ Car\ P = v_{P} = -78\ km/h[/tex]

And the absolute velocity of Barbara's Car is given as:[tex]Absolute\ Velocity\ of\ Barbara's\ Car = v_{B} = 52\ km/h[/tex]

Now, for the velocity of Car p with respect to the velocity of Barbara's Car can be given s follows:

[tex]Velocity\ of\ Car\ P\ measured\ by\ Barbara = v_{PB} = v_{B}-v_{P}\\\\v_{PB} = 52\ km/h-(-78\ km/h)[/tex]

[tex]v_{PB} = 130\ km/h[/tex]

Explanation:

Single slit diffraction

Diffraction is the phenomenon of spreading out of waves as they pass through an aperture or around objects. Diffraction occurs when the size of the aperture or obstacle is of the same order of magnitude as the wavelength of the incident wave. For very small aperture sizes, the vast majority of the wave is blocked. in case of  large apertures the wave passes by or through the obstacle without any significant diffraction.

Answer: D

Explanation:

Answer:

T = 10 s

Explanation:

First, we need to find the frequency of the object as follows:

[tex]Frequency = f = \frac{Speed\ in\ rpm}{60}[/tex]

where,

Speed = Angular Speed = 6 rpm

Therefore,

[tex]f = \frac{6\ rpm}{60}\\\\f = 0.1\ Hz[/tex]

Now, for time period (T):

[tex]Time\ Period = T = \frac{1}{f}\\\\T = \frac{1}{0.1\ Hz}\\\\[/tex]

T = 10 s

Answer:

Maximum=70 m

Minimum=26 m

Explanation:

Vector Addition

Since vectors have magnitude and direction, adding them takes into consideration not only the magnitudes but also their respective directions. Two vectors can be totally collaborative, i.e., point to the same direction, or be totally opposite. In the first case, the magnitude of the sum is at maximum. Otherwise, it's at a minimum.

Thus, the maximum magnitude of the sum is 48+22 = 70 m and the minimum magnitude of the sum is 48-22= 26 m

Answer:

Explained below

Explanation:

For a velocity time graph, the y - axis will represent velocity while the x - axis will represent time.

Now, to calculate velocity at a certain time t, we will draw a perpendicular line from the time on the x-axis to the graph line and trace the horizontal line from that point to the y-axis which will give the corresponding velocity at that time.

Now, for the acceleration at a time t. After getting the velocity like explained above, we now divide the velocity by the time.

Answer:

0 j

Explanation:

The work done by the employee on the box at the given zero displacement is 0 J.

The given parameters;

The work done by the employee on the box is calculated as follows;

W = Fd

where;

Since the employee sits on the box without moving it, the distance moved by the box = 0

W = 500 x 0

W = 0 J

Thus, the work done by the employee on the box is 0 J.

Learn more about work done and displacement here: https://brainly.com/question/8635561

Answer:

Yes it is matter

Explanation:

In physics, usually the word "electricity" isn't really used. "Electric current" is more common, and is defined as the flow of charges, where the charges are held by particles (electrons). Electrons have mass, so they are definitely matter.

Answer:

4.535 N.m

Explanation:

To solve this question, we're going to use the formula for moment of inertia

I = mL²/12

Where

I = moment of inertia

m = mass of the ladder, 7.98 kg

L = length of the ladder, 4.15 m

On solving we have

I = 7.98 * (4.15)² / 12

I = (7.98 * 17.2225) / 12

I = 137.44 / 12

I = 11.45 kg·m²

That is the moment of inertia about the center.

Using this moment of inertia, we multiply it by the angular acceleration to get the needed torque. So that

τ = 11.453 kg·m² * 0.395 rad/s²

τ = 4.535 N·m

The Torque will be "4.535 N.m".

Given:

Mass of ladder,

Length of ladder,

The moment of inertia will be:

→ [tex]I = \frac{mL^2}{12}[/tex]

     [tex]= \frac{7.98\times (4.15)^2}{12}[/tex]

     [tex]= \frac{7.98\times 17.2225}{12}[/tex]

     [tex]= 11.45 \ kg.m^2[/tex]

hence,

The torque will be:

→ [tex]\tau = 11.453\times 0.395[/tex]

      [tex]= 4.535 \ N/m[/tex]

Thus the above approach is correct.      

Learn more about torque here:

https://brainly.com/question/19247046

Answer:

no

gravitational force between them is far smaller than the frictional force between the guy and the bench