32. A force of 63.0 N is applied to a 6.70 kg block at rest. If the block travels 138 m in the first 6.00

seconds the force is applied, what is the average force of friction acting on the block?

33. An 18.0 N force is applied to a 5.00 kg object at rest. As a result of the force the object moves 6.00m in 2.00 s.

a) Calculate the actual acceleration. b) What acceleration is predicted by Newton's law? c) What force of friction is acting on the object?

34. A dynamics cart with a mass of 4.00 kg is being pulled across a horizontal table by a force of 14 N. a) At what rate would you expect the cart to accelerate, neglecting friction? b) If the cart started at rest and travelled 24.0 m in the first 4.00 s, what force of friction must have been acting?

35. A 4.00 kg object initially at rest on a horizontal surface is acted on by a 16.0 N force. In 3.00 seconds, the mass moves 13.5 meters.

a) What is the actual acceleration? b) What acceleration is predicted by Newton's law? c) Explain the difference in the above two accelerations.

36. What constant retarding force must be applied to a 6.25 kg block moving at 13.0 m/s to slow it down to 5.00 m/s in a distance of 4.50 m? The force of friction between the block and the horizontal surface on which it is sliding is 75.0 N.

37 What is the mass of a car if a braking force of 3.10 x 104 N is required to slow it down from 30.0 m/s to 6.00 m/s in a distance of 27.0 m? The force of friction acting is 9.00 x 103 N.

38 What constant force must be applied to a 4.00 kg object initially moving at 20.0 m/s on a horizontal surface if it is to move 175 meters in 5.00 seconds and the force of friction between the object and the surface is 6.00 Newtons?

39. A 1500 kg car is moving at 12.5 m/s when the brakes are applied resulting in a net force of 4500 N opposing the motion of the car. How fast will the car be moving at a distance of 24. 0 m from the point when the brakes were applied?

40. A 35.5 kg object is moving with an initial velocity of 3.00 m/s. If it is acted on by a net force of 142 N, how long will it take to travel 65.0 m?

C. Challenging Problems

41. A 1.00 kg toy car is moving across a smooth floor with a velocity of 5.00 m/s. An unbalanced force of 2.00 N, opposite to the direction of motion, acts on the car for 4.00 s. Calculate how far the car will be from its initial position at the end of the 4.00 s.

42. A 1.50 kg block is at rest on a horizontal surface. The force of friction between the block and the surface is 3.00 N. The block is pulled by a force of 7.50 N for a distance of 13.5 m and then it is released. How far will it be from its starting point 5.00 s after it started to move?