<span>Velocity of boy with which it hits the ground is

v = √(2gH)

= √(2 × 10 m/s^2 × 3 m)

= √(60) m/s

Boy will not rebound.

So,

change in momentum = mv - 0

= Mass of boy × √(60) m/s

So the answer would be C – best estimate.</span>

**Answer:**

N

**Explanation:**

= initial velocity of the bullet = 0 m/s

= final velocity of the bullet as it leaves = 443.4 m/s

= acceleration of the bullet

= length of the barrel of the rifle = 0.7 m

the kinematics equation we can use must include the variables in the above list, hence

ms⁻²

= mass of the bullet = 7.9 g = 0.0079 kg

Force exerted on the bullet is given as

N

**Answer:**

The answer is D.

**Explanation:**

They vibrate parallel to the wave.

During the propagation of a sound wave in air, the vibrations of the particles are most accurately represented as longitudinal. Longitudinal waves are waves in which the motion of the individual particles of the medium occurs in a direction that is **parallel **to the direction of energy transmission.

**Explanation:**

a) The process can be modeled as an adiabatic compression, because the pulses of pressurized air is governed into the tire and time frame is very small for any heat transfer through the tires. Hence, Q_net = 0.

The first law of thermodynamics states that the change in the internal energy is ∆U=Q-W= -W, since Q_net = 0 for adiabatic processes. Work is being done on the system by pumping action hence W_net is negative; therefore the change in the internal energy, ∆U, is positive. Since ∆U, is a function of initial and final temperatures the final final temperature must increase for ∆U to be positive.

b) The process can be modeled as an adiabatic expansion when a highly pressurized mixture of air and water is released into atmosphere from 20 atm to 1 atm. The time frame is very small for any heat transfer through the mixture. Hence, Q_net = 0.

The first law of thermodynamics states that the change in the internal energy is ∆U=Q-W= -W, since Q_net = 0 for adiabatic processes. Work is being done by the mixture on its surroundings due to change in pressure from high to low. The W_net is positive; therefore the change in the internal energy, ∆U, is negative. Since ∆U, is a function of initial and final temperatures the final final temperature must decrease for ∆U to be negative. The final temperatures drops below freezing point due to sudden adiabatic expansion of mixture leads to formation of snow.