## Py 120 Test 1 Spring 1998

Name: _____________________ Pledged:___________________________

### Part A: Interactive Problem. (20 Pts)

1. Sketch the position, velocity, and acceleration as a function of time for 10 seconds for the ball shown on the computer monitor. Assume it takes the ball 2 seconds to move between the two walls. Begin

### Part B: Concept problems. (15 Pts each.) These are short but you must still GIVE YOUR REASONS.

1. Two stones are released from rest at a certain height, one after the other.

a) Will the difference in their speeds increase, decrease, or stay the same?

b) Will their separation distance increase, decrease, or stay the same?

c) Will the time interval between the instants when they hit the ground be smaller than, equal to, or greater than the time interval between the instants of their release?
2. A basketball player is jumping vertically upward.

a) Draw a free body diagram of the play's body and the earth. Use the length of your arrows to show the relative magnitude of the various forces the moment the player has flexed her legs and is starting upward-- but still in contact with the floor.

b) Repeat after the player breaks contact with the floor.

c) Repeat at the top of the jump.

### Part C: Textbook problems (25 Pts each.)

1. A projectile is fired from a cannon at an angle of 30 degree with a speed of 20 m/sec. Where is the projectile one half, ½, second after it is fired and how fast is it going?
2. A block is given an initial push up an incline plane with an initial velocity of 6 meter/sec. The plane makes an angle of 20 degree with respect to the ground.

a) How far up the incline does the block travel if the surface is frictionless.

b) How far up the incline does the block travel if the coefficient of friction is 0.5?

c) (5 Pts extra credit) How long does it take for the block to return to its original position at the bottom of the incline? Include friction in your analysis.