Physics 201 MWF10:20 Fall 2001 (Ford)

Exam I Chapts 1--4 Cutnell and Johnson 5th ed


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

(3 pts) 1. Two forces are applied to a box. One force has magnitude 3 N and direction due east. The second force has magnitude 4 N and direction due north. The magnitude of the net force on the box is

a) 1 N
b) 3 N
c) 4 N
d) 5 N <---------
e) 7 N


(3 pts) 2. You throw a ball straight up into the air. As the ball travels upward, from just after it is released until it reaches its maximum height, its speed is decreasing. During this part of the motion the acceleration of the ball is

a) zero
b) downward <---------
c) upward


(4 pts) 3. A baseball is thrown with an initial speed of 30 m/s at an angle of 53° above the horizontal. When the baseball reaches its maximum height its speed is

a) zero
b) 18 m/s <---------
c) 24 m/s
d) 30 m/s


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) 4. A dog runs horizontally with a speed of 2.0 m/s off a platform that is 12.0 m above the surface of the water.


a) How much time elapses from when the dog leaves the edge of the platform until he strikes the water?

Ans. ______1.56 s_____________

b) What is the horizontal distance from the edge of the platform to the point where the dog strikes the water?

Ans. _____3.12 m__________


(16 pts) 5. You are a passenger on a boat that is traveling relative to the earth at a constant speed of 8.0 m/s in a direction 37° north of west. A seagull is traveling relative to you due east at a speed of 3.0 m/s. What are the magnitude and direction of the velocity of the seagull relative to the earth? Your answer must include a clearly labeled velocity addition diagram.

Ans. magnitude _____5.9 m/s____

direction ___54.7° N of W or 35.3° W of N____


(16 pts) 6. Two soccer players, Bob and Jill, start from rest 60 m apart. At the same instant they start to run towards each other. Bob runs with a constant acceleration that has magnitude 0.50 m/s² and Jill runs with a constant acceleration that has magnitude 0.30 m/s².

a) How far does Bob run until they collide?

Ans. _____37.5 m________

b) What is Jill's speed just before she collides with Bob?

Ans. _______3.7 m/s____


(20pts) 7. Consider the system shown in the sketch. A block of mass m₁ rests on a frictionless tabletop and is connected by a light rope that passes over a massless, frictionless pulley to a hanging block of mass 5 kg. A horizontal force P = 90 N, directed to the left, is applied to the block on the tabletop and this block accelerates to the left with a = 2.0 m/s².


a) While the blocks are moving, what is the tension T in the rope that connects the two blocks?

Ans. ______59 N____

b) What is the mass m₁ of the block on the tabletop?

Ans. _____15.5 kg___


(20 pts) 8. A 10-kg box is being pulled down a ramp by a force P = 10 N that is parallel to the ramp. The ramp is inclined at 37° with respect to the horizontal. The coefficient of kinetic friction between the ramp and the box is 0.4.


a) What is the magnitude of the friction force that acts on the box?

Ans. ____31.3 N____

b) What is the acceleration a of the box?

Ans. ____3.75m/s²_____