Task 4 Leonard Physics Review

Car A with a mass of 2000 kg traveling to the right at an unknown speed collides head-on with Car B of mass 1500 kg traveling to the left at 5 m/s.  If the cars stick together after impact and move to the left at 1 m/s, how much kinetic energy is lost during the collision?

• 1750 J

• 18750 J

• 21000 J

• 22750 J

A 0.03 kg tennis ball moving at 15 m/s strikes a tennis racket and rebounds at 10 m/s in the opposite direction, as shown above. The ball is in contact with the racket for 0.030 s.  What is the magnitude of the average force exerted by the racket on the ball?

• 5 N

• 10 N

• 25 N

• 50 N

A block of mass 1 kg slides on a frictionless, horizontal surface with a velocity of 3.0 m/s to the right, as shown above, and collides with a block of mass 3 kg that is at rest.  As a result of the collision, the 1 kg block moves to the left with a speed of 0.5 m/s. Which of the following correctly states whether the collision is elastic or inelastic and provides a valid justification?

• Elastic, because the total momentum before the collision equals the total momentum after.

• Elastic, because the initial kinetic energy is the same as the final kinetic energy.

• Inelastic, because the total momentum before the collision does not equal the total momentum after.

• Inelastic, because some of the initial kinetic energy is converted into nonmechanical energy.

How does an air bag protect a passenger involved in a car crash?

• It reduces the kinetic energy loss of the passenger

• It reduces the momentum change of the passenger

• It shortens th stopping time of the passenger and increases the force applied during the crash

• It lengthens the stopping time of the passenger and reduces the force applied during the crash

A 2 kg object traveling at 5 m/s on a frictionless horizontal surface collides head-on with and sticks to a 4 kg object initially at rest. What is the resulting speed of the objects after the collision?

• 1.67 m/s

• 2 m/s

• 2.5 m/s

• 5 m/s

Two blocks are on a horizontal frictionless surface. Block A is moving with an initial velocity of V₀ toward Block B, which is stationary , as shown above. The two blocks collide, stick together, and move off with a velocity V₀ /2. Which block, if either, has the greater mass?

• Block A

• Block B

• Neither; their masses are the same

• The answer cannot be determined without the mass of one of the blocks.