Will someone please help me with this physics questions.

Question

A 1,000 kg car is traveling at 20 m/s. The driver applies the brakes over a 10 s time period. What is the magnitude of the braking force?

a. 1000 N

b. 4000 N

c. 3000 N

d. 2000 N

A moving billiard ball collides with an identical stationary billiard ball in an elastic collision. After the collision, the second ball has the same speed that the first ball had originally. Which of the following is true of the first ball after the collision?

a. It comes to rest.

b. It maintains half of its initial velocity.

c. It moves in the opposite direction of its original motion.

d. It maintains its initial velocity.

Answer 1

Answer (d)

F = ma - Newton's second law.

a = v/ t - kinematics formula.

a = 20 m/s / 10 s = 2 m/s² F = 1000 kg x 2 m/s² = 2000 N

Answer (a)

This follows from the applying the law of conservation of linear momentum and the law of conservation of mechanical energy to the elastic collision of the bodies. If masses are the same, then if one of the bodies was at rest and another was moving, after the collision they exchange their velocities. It means that the body, that was moving, will stop. And the one that was at rest, starts to move with the velocity of the collided body.