Physics 201 MWF10:20 Fall 2003 (Ford)

Exam II Chapts. 5-7 in Cutnell and Johnson 6th ed


Multiple Choice questions. Circle the correct answer. No work needs to be shown.

(3 pts) 1. When an object travels from point A to point B, its kinetic energy increases. The total work done on the object during its motion from A to B is

(a) positive <--------
(b) negative
(c) zero


(5 pts) 2. A rock with mass 20 kg lands in a 40 kg wagon that is initially at rest on a horizontal, frictionless surface. Just before the rock lands in the wagon the rock is traveling at 15 m/s in a direction 60° below the horizontal. What is the speed of the wagon after the rock has landed in it?

(a) zero
(b) 1.00 m/s
(c) 2.50 m/s <---------
(d) 3.75 m/s
(e) 5.00 m/s


(4 pts) 3. When a rock moves from point A to point B, its gravitational potential energy increases. The work done on the object by gravity as the object moves from A to B is

(a) positive
(b) negative <--------
(c) zero


(4 pts) 4. A satellite with mass 20 kg is in a circular orbit around a planet with unknown mass. The radius of the orbit of the satellite is 5.0 × 10⁶ m and the speed of the satellite is 8000 m/s. What is the magnitude of the gravitational force exerted on the satellite by the planet?

(a) zero
(b) 144 N
(c) 196 N
(d) 256 N <----------
(e) 512 N


(4 pts) 5. A 5.0 kg block slides 8.0 m down a 37.0° incline, from point A to point B. During this motion the work done by the normal force on the block is



(a) +49 J
(b) zero <----------
(c) +235 J
(d) -235 J
(e) +313 J
(f) -313 J
(g) +392 J
(h) -392 J


On the following four problems show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.

(20 pts) 6. A box of mass 5.0 kg is pulled up a hill by a force P. At point A the speed of the box is 2.0 m/s and at point B the speed is 5.0 m/s. Point B is a vertical height of 6.0 m above point A. The force P does 420 J of work on the box as the box moves from point A to point B. How much work does friction do on the box as it moves from A to B?



Ans. ____-73.5 J___



(20 pts) 7. A small block with mass 0.20 kg is sliding without friction inside a circular track that has radius 3.0 m. The path of the block is a vertical circle. As the block slides through the lowest point of its path, point A in the sketch, the normal force the track exerts on the block is 14.0 N. What is the speed of the block at the highest point of the path, point B in the sketch?



Ans. ____7.94 m/s_____


(20 pts) 8. A rock of mass 0.40 kg swings in a horizontal circle with constant speed on the end of a string that is 2.0 m long. The string makes a constant angle of 53° with the vertical.



a) What is the tension in the string?

Ans. _____6.51 N____

b) What is the magnitude of the acceleration of the rock?

Ans. ____13 m/s²_____

c) What is the speed of the rock?

Ans. ____4.56 m/s___



(20 pts) 9. A rock with mass 0.50 kg is sitting at rest on a horizontal, frictionless surface. A bullet with mass 0.020 kg is traveling due east with a speed of 200 m/s. The bullet hits the rock, and after it bounces off the bullet is traveling due north with a speed of 140 m/s. What are the magnitude and direction of the velocity of the rock just after the bullet has bounced off?



Ans. magnitude ____9.77 m/s______

direction ___35° south of east_____