Physics 201 MWF10:20 \qquad Fall 2003

Exam I Chapts. 1-4 in Cutnell and Johnson 6th ed.


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

(4 pts) 1. You are standing in an elevator that is traveling upward and slowing down. The normal force the floor of the elevator exerts on you is

(a) the same as your weight
(b) greater than your weight
(c) less than your weight


(4pts) 2. From the edge of the roof of a 20-m tall building you throw two rocks. Rock A is thrown straight up with initial speed 8 m/s; it doesn't hit the roof on the way down and eventually strikes the ground. Rock B is thrown straight down with initial speed 8 m/s. Air resistance can be neglected. What can you say about the speeds of A and B just before they strike the ground?


(a) they have the same speed
(b) the speed of A is greater than the speed of B
(c) the speed of B is greater than the speed of A


(4 pts) 3. A ball is projected on level ground with a speed of 50 m/s at an angle of 53° above the horizontal. If air resistance is neglected, what is the speed of the ball when it is at its maximum height?

(a) 0
(b) 10 m/s
(c) 20 m/s
(d) 30 m/s
(e) 40 m/s
(f) 50 m/s


(4 pts) 4. A truck is traveling east and speeding up. A box sits on the flat bed of the truck and is at rest relative to the truck. The direction of the friction force on the box is

(a) east
(b) west
(c) the friction force is zero
On the following four problems show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.


(18 pts) 5. A small rock is thrown straight up from the roof of a building. The rock has an initial speed of 29.4 m/s and strikes the ground 8.0 s after it is thrown. Neglect air resistance.


a) What is the maximum height above the roof reached by the rock?

Ans. ________________________

b) What is the height of the building

Ans. _____________________


(22 pts) 6. A small rock is projected from the ground toward a building that is a horizontal distance of 30.0 m from the initial position of the rock. The rock has an initial velocity that has magnitude 25.0 m/s and direction 37° above the horizontal. Neglect air resistance.


a) What vertical distance above the ground does the rock strike the building?

Ans. ______________________

b) What is the speed (magnitude of the velocity) of the rock just before it strikes the building?

Ans. _____________________


(20 pts) 7. Maria is running at constant velocity. She observes a soccer ball traveling at a constant velocity of 8.0 m/s due west relative to her. Her teammate, who is standing still relative to the ground, measures that the ball is traveling at 6.0 m/s at an angle of 37° south of east. What is the velocity (magnitude and direction) of Maria relative to the earth?

Ans. magnitude ________________


direction _____________

(24 pts) 8. A 20.0 kg block is on a 37° incline. A light rope that passes over a light, frictionless pulley connects the 20.0 kg block to a block of mass m that is suspended vertically. The coefficient of kinetic friction between the 20.0 kg block and the incline is 0.4. The system is released from rest, and the blocks move. While the blocks are moving, the tension in the rope is 20.0 N.


a) What is the acceleration of the 20.0 kg block?

Ans. __________________

b) What is the mass m of the other block?

Ans. ____________________