Homework 2

1. A 12 g bullet accelerates from rest to 600 m/s in a gun barrel of length 12 cm. Find the accelerating force (assuming it constant). 2. A horizontal cable pulls a trailer of mass 300 kg along a horizontal track. If the tension in the cable is 700 N. (a) Starting from rest, how long will it take

the trailer to reach a speed of 15 m/s? (b) Find the distance covered during this time.

3. The force acting on a particle varies as shown in Figure 1. Find the work done by the force on the particle as it moves:

(a) From x = 0 to x = 7.0 m.

(b) From x = 7.0 m to x = 10.0 m.

(c) From x = 0 to x = 11.0 m.

Fig.1

4. In the track shown in Fig. 2, section AB is a quadrant of a circle of radius r = 1 m. A block is released at A and slides without friction until it reaches point B, then moves a distance d = 4m on a horizontal rough plane before stopping at point C. (a) How fast is the block moving at point B? (b) What is the

coefficient of kinetic friction between the block and the plane?

Fig. 2

5. Two blocks of masses 5 kg and 10 kg are in contact on a smooth horizontal surface. A horizontal force of magnitude 15 N pushes them from left to right (a) Find the magnitude of the acceleration of the system, (b) Find the magnitude of the reaction force between the blocks.

6. A block moves up an incline of angle 25° under the action of the three forces. One force of 40 N is applied horizontally, another force of 20N is applied parallel to the incline and the last force of 15 N is applied perpendicular to the incline. Find the work done by each force as the block moves a distance of

2m up the incline.

7. A small ball of mass m is attached to a massless thread that is fixed to the roof of a car. (a) Find the angle does the thread make with the vertical when the car has a constant acceleration of 5 m/s2. (b) What is the angle when the car is moving at constant velocity of magnitude v = 50 km/h?