A 2 000-kg car is slowed down uniformly from 20.0 m/s to 5.00 m/s in 4.00 s. (a) What average force acted on the car during that time, and (b) how far did the car travel during that time?

Question 5: A ball of mass m collides with a wall with initial velocity -voj (and then it rebounds). The force acting on the ball by the wall during the collision is given by F = (At + Bt²)j where A and B are positive constants. Find the velocity of the ball after the collision. The ball is in contact with the wall 10-2 seconds (Assume that the gravitational force is negligible compared with force F).

A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially  with a speed of 15 ms–1. How long does the body take to stop?

a 925-kg pick up decelerates to rest from a speed of 97.5 km/h in a distance 125 m. Suppose the pick up is initially traveling in the positive direction. suppose instead of breaking that the pick up hits a concrete abutment at full speed is brought up to a stop at 2.0 m. Calculate the force in newtons exerted on the pickup in this case.

When starting a foot race, a 70.0-kg sprinter exerts an average force of 650 N backward on the ground for 0.800 s. (a) What is his final speed?

On a test flight a rocket with mass 400 kg blasts off from the surface of the earth. The rocket engines apply a constant upward force F until the rocket reaches a height of 100 m and then they shut off. A) If the rocket is to reach a maximum height of 400 mm above the surface of the earth, what value of F is required? Assume the change in the rocket's mass is negligible. (Express your answer with the appropriate units.)

A child sits in a wagon with a pile of0.34-kg rocks. If she can throw each rock with a speed of 9.5 m>srelative to the ground, causing the wagon to move, how manyrocks must she throw per minute to maintain a constant averagespeed against a 3.4-N force of friction?

(1) A car with mass 996 kg moving at 28 m/s hits a giant bag of marshmallows.  The bag slows the car down, but it is unable to completely stop it because it ruptures at Dt = 1.8 s after the car hits, scattering marshmallows all over the countryside.  Suppose the bag exerts a force on the car that depends on time (t) given by F = -At2; A = 7.2 x 103 N/s2 when t is in seconds   (2) Two objects, moving towards each other with speed v, collide head on, stick together, and then move on with speed v/4 after the collision. (a) What is the ratio of the kinetic energy after the collision to the kinetic energy before the collision? (answer: 1/16) (b) What is the ratio of the mass of the more massive object to the mass of the less massive object? (answer: 5/3)

A particle is at rest. At t=0 a force F= F bēgins to act.on it. As the particle moves its mass varies with time as m = m, 1--]. Speed of the partičle after time t== becomes (2) ¿ m, 3r. F 2 mg Fo (b) 27 m. F (d) 2m, (1) *