1. A crate is pulled across a horizontal floor by a rope tied to the crate. The rope makes an angle of 37 degrees with the horizontal. Find the frictional force if the tension in the rope is 10 N and the crate moves with constant velocity.
a. 3 N
b. 5 N
c. 7 N
d. 8 N
e. none of them
Answer: _____
2. A crate slides down a 35° ramp with constant speed. What is the coefficient of kinetic friction between the crate and the ramp?
a. 0.25
b. 0.45
c. 0.50
d. 0.60
e. 0.70
Answer: _____
3. The coefficient of static friction between the tires of a car and asphalt is 0.77. Which of these is the steepest angle of a slope on which the car can be parked?
a. 23°
b. 30°
c. 37°
d. 45°
Answer: _____
4. A 500 N weight is hung at the middle of a rope attached to two buildings at the same level. The cable will break if the tension exceeds 1800 N, what is the minimum angle the rope can make with the horizontal?
a. 4°
b. 8°
c. 11°
d. 18°
Answer: _____
5. Sam is using a rope to pull a box weighing 300 N across a floor with constant velocity. The rope makes an angle of 30° above the horizontal. If the tension in the rope is 100 N, what is the normal force exerted by the floor on the box?
a. 300 N
b. 290 N
c. 270 N
d. 250 N
Answer: _____
6. A 5 kg block is pulled horizontally across a floor by a string attached to it with an acceleration of 2 m/s2. What is the tension in the string if the coefficient of sliding kinetic friction between the block and floor is 0.20?
a. 5.6 N
b. 9.8 N
c. 20 N
d. 29 N
Answer: _____
7. A force of 250 N pushes a 50 kg box along a horizontal surface. The force is directed 300 below the horizontal. What is the acceleration of the box if the coefficient of kinetic friction between the box and the surface is 0.30? (Since the possible answers given are written to two digits of accuracy, use g = 9.8 m/s2.)
a. 0.64 m/s2
b. 1.8 m/s2
c. 3.2 m/s2
d. 6.3 m/s2
Answer: _____
8. The word "normal" in the phrase "normal force" indicates that:
a. the force is exerted by a surface
b. the force is exerted by an object
c. the force exerted by a surface is parallel to itself
d. the force exerted by a surface is perpendicular to itself
Answer: _____
9. A 1.50 kg mass is acted upon by a force of 16.0 N applied at an angle of 600 above the horizontal. What is the acceleration of the mass? (Since the possible answers given are written to three digits of accuracy, use g = 9.81 m/s2.)
a. 4.33 m/s2
b. 5.36 m/s2
c. 6.33 m/s2
d. 7.35 m/s2
Answer: _____
10. A weight of 5000 N is suspended by two cables. The object is at rest. The first cable is horizontal and the second makes an angle of 143° with the first cable. Find the tension of the first cable.
a. 4000 N
b. 6640 N
c. 8310 N
d. 3340 N
Answer: _____
11. Two blocks with masses 2.00 kg and 4.00 kg are placed side-by-side on a frictionless horizontal surface. A horizontal force with a magnitude of 5.20 N is applied to the 2.00 kg block perpendicular to its surface. What is the magnitude of the force on the 4.00 kg block?
a. 2.60
b. 3.11
c. 3.47
d. 3.89
Answer: _____
12. A 43 kg child sits in a massless swing. With what horizontal force must the seat be pulled so that the ropes form an angle of 35° with respect to the vertical?
a. 300 N
b. 320 N
c. 340 N
d. 360 N
Answer: _____
13. A physics student holds a 2.4 kg block against a wall by pressing on it perpendicularly to the wall. Find the minimum force she must exert if the coefficient of static friction is 0.32.
a. 7.5 N
b. 74 N
c. 24 N
d. 24 N
e. not enough information
Answer: _____
14. A pair of “fuzzy dice” hangs from a string attached to the rear view mirror of a race car moving with constant acceleration. Find the acceleration if the string makes a 70° angle with the vertical.
a. 22 m/s2
b. 27 m/s2
c. 33 m/s2
d. 35 m/s2
e. 39 m/s2
Answer: _____
15. A laptop computer sits on the horizontal surface of the seat of a car moving at 8.0 m/s. The driver starts slowing down to stop. Find the minimum stopping distance so the computer does not slip and fall onto the floor if the coefficient of static friction between the seat and the laptop is 0.40 and the coefficient of kinetic friction is 0.20.
a. 4 m
b. 8 m
c. 12 m
d. 16 m
e. 24 m
Answer: _____
16. Two forces act on a 5 kg object. One force is 40 N and directed east. The other force is directed west. The acceleration of the object is 3 m/s West. What is the magnitude and direction of the second force?
a. 15 N West
b. 55 N West
c. 25 N East
d. 55 N East
Answer: _____