Download Coefficient of Friction Worksheet

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Net force and Coefficient of Friction Worksheet
1. Suppose a 10 N force is applied to the side of a 4.0 kg block that is sitting on a table. The block experiences a
frictional force against the force that is applied.
a.
b.
c.
d.
e.
f.
g.
Draw a free body diagram for the block?
What is the weight of the block (FG)?
What is the normal force on the block (FN)?
If the coefficient of kinetic friction is μk = .20, what is the frictional force on the block (Fk)?
What is the net force on the block?
What is the acceleration of the block from the net force?
What would be the minimum value of the coefficient of static friction in order for the block to remain
motionless?
2. A block weighing 300 N is moved at a constant speed over a horizontal surface by a force of 50 N applied
parallel to the surface. What does the “constant speed” tell you about the forces acting on the block?
a. Draw a free body diagram for the block.
b. What is the coefficient of kinetic friction (μk)?
c. What is the mass of the block?
d. What would be the acceleration of the block if μk = 0?
3. Two forces act on an object at the same time. F1 = 100 N [30 o N of E] and F2 = 200 N [45 o N of W]. Find the
net force. What is the equilibrant force? (What is the forth force that could balance them out to a state of
equilibrium?)
4. A 2kg basketball is thrown upward for a toss up at the beginning of a basketball game. Just before it leaves the
officials hand the ball has an upward force of 75N. What is the net force on the ball?
5. You are moving to a new house. You are pushing a refrigerator on a dolly up a ramp. You are pushing up
1600N at and angle of 30degrees to horizontal. The refrigerator is 200kg. What is the normal force of the
refrigerator? What is the net force on the refrigerator?
6. There is a cell phone tower that you are in charge of putting up. You already have 2 guide wires on. Looking
down, one with 80N @ 15degrees, the second with 100N @ 90degrees. What is equalizing force?
7. A woman exerts 100. N of force to lift a laundry basket weighing 75 N. At what rate is the basket accelerated
upward?
8. A hockey puck has a coefficient of kinetic friction of μk = .60. If the puck feels a normal force (FN) of 10 N,
what is the frictional force that acts on the puck? What is the mass of the puck?
9. A large box is being dragged across the floor at constant velocity. If the box has a
mass of 60 kg and it takes a 50 N force, acting horizontally, to drag the box, what
is the coefficient of friction?
10. A bolder of mass 45 kg is pushed on a surface with a coefficient of kinetic friction
of 0.85. What force has to be applied to produce an acceleration of 2 m/s2?
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11. The picture below shows the forces acting on a block that is
accelerating to the right along a level table. Treat the handle as
part of the block. Friction is also present.
a. Draw the free body diagram for the following picture.
12. On takeoff, the propeller of a helicopter exerts a minimum of
8000-N of force on the helicopter, directed upward at an angle of 65 degrees above the horizontal. The
helicopter rises with constant velocity in the vertical direction while continuing to accelerate in the horizontal
direction.
a. What is the weight of the helicopter?
b. What is the horizontal acceleration?
13. A person has a reasonable chance of surviving an automobile crash if the deceleration is no more than 30 "g's"
(thirty times the acceleration due to gravity)
a. Calculate the force on a 70 kg person accelerating at this rate.
b. What distance is traveled if the person comes to rest from 80 km/hr with this acceleration?
14. A girl coasts down a hill on a sled, reaching the bottom with a speed of 7.0 m/s. If the coefficient of friction
between runners and snow is 0.050 and the girl and sled together weigh 600 N. how far does the sled travel on
the level surface before coming to a stop? (Hint* Solve for acceleration then think four kinematic
equations)
15. A desk has a mass of 71.25 kilograms. If the coefficient of static friction between the desk and the floor is 1.14,
what force must be used to move the desk from rest?
16. A 100 N force is applied to the side of a crate resting on a level floor. The crate has a mass of 50 kg. If the
coefficient of static friction is μs = .25, is the 100 N force enough to make the crate accelerate? Explain why or
why not. (As always, start with a force diagram)
17. Three forces act on an object at the same time. F1 = 10 N [E], F2 = 15 N [N] and F3 = 15 N [S]. What is the
net force? What is the equilibrant force?
18. A 52 N sled is pulled across a cement sidewalk at constant velocity. A horizontal
force of 36 N is exerted. What is the coefficient of kinetic friction.
19. A refrigerator is placed on a ramp. The refrigerator begins to slide when the ramp is raised to an angle of 34°.
What is the coefficient of static friction?
20. A hockey player exerts a force of 80. N with his hockey stick on a stationary puck of mass 500g.
a. At what rate will the puck accelerate while in contact with the stick?
b. If the stick exerts the force on the puck for 0.70 s, at what speed will the puck leave the face of the hockey
stick?
c. What distance would the puck travel?
21. Your pet gorilla want a ride in his little red wagon. (Don’t ask.) So you pull him with a force of 175N at an
angle of 35°. Your gorilla has a mass of 250kg and the is a coefficient of friction between his wagon and the
sidewalk is 0.8. How fast is your gorilla accelerating?
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Challenging!!!
22. A box weighs 2000. N. It is accelerated uniformly over a horizontal surface at a rate of 8.00 m/s2. The
opposing force of friction between the box and the surface is 27.4 N.
a. How much force is exerted horizontally on the box?
b. How much force would be required to LIFT the box upward with an acceleration of 8.00 m/s2?
23. A person whose mass is 75 kg is lowered with a rope down the side of a cliff. The rope being used can support
a maximum of 595 N. In order to prevent the rope from breaking, at what minimum rate must the person
accelerate?
24. A packing crate is placed on a plane inclined at an angle of 35° from horizontal. If the coefficient of static
friction between the crate and the plane is 0.65, will the crate slide down the plane?
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