Download Friction Problems

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Extra Problems – FRICTION
1. A smooth wooden block is placed on a smooth wooden tabletop. A force of
14.0 n is necessary to keep the 40.0 n block moving at a “constant velocity”.
a. What is the coefficient of sliding friction for the block and table?
b. If a 20.0 n weight is placed on the block, what force would be required
to keep the block and weight moving at “constant velocity”?
[0.350]
[21.0 n]
2. A 52 n sled is pulled across a cement sidewalk at “constant speed”. A
horizontal force of 36 n is exerted. What is the coefficient of sliding friction
between the sidewalk and the metal runners of the sled?
[0.69]
3. Suppose the sled in exercise 2 is on packed snow. The coefficient of friction
is now only 0.12. If a person weighing 560 n sits on the sled, what force is
needed to slide the sled across the snow at “constant speed”?
[84 n]
4. The coefficient of sliding friction between rubber tires and wet pavement
is 0.50. The brakes are applied to a 750 kg car traveling 30 m/s and skids
to a stop.
a. What is the size and direction of the force of friction that the road exerts
on the car?
b. What would be the size and direction of the acceleration of the car?
c.
How far would the car travel before stopping?
[-3700 n]
[-4.9 m/s2]
[92 m]
5. A block weighs 2000 n. If a horizontal force of 100 n is required to keep it
in motion with “constant speed” on a horizontal surface, what is the
coefficient of sliding friction?
[0.0500]
6. In a coefficient of friction experiment, a horizontal force of 45 n was needed
to keep an object weighing 125 n sliding at “constant speed” over a horizontal
surface. Calculate the coefficient of sliding friction.
[0.36]
7. A crate weighing 1250 n slides down an inclined plane at “constant speed”.
The plane is 6.0 m long. Its height is 3.0 m. What is the coefficient of
sliding friction between the crate and the inclined plane?
[0.579]
8. The coefficient of sliding friction between a metal block and the inclined
surface over which it will slide is 0.200. If the surface makes an angle of
20.0 with the horizontal and the block has a mass of 80.0 kg, what force
is required to slide the block at a “constant speed” up the plane?
[415 n]
9. A crate weighing 400 n is pulled along a horizontal sidewalk at “constant
speed” by a rope that makes an angle of 45.0 with the sidewalk. If a force
of 150 n is applied to the rope, what is the coefficient of sliding friction?
[0.361]
10. A box having a mass of 50.0 kg is dragged across a horizontal floor by means
of a rope tied to the front of it. The coefficient of sliding friction between the
box and the floor is 0.300. If the angle between the rope and the floor is 30.0,
what force must be exerted on the rope to move the box at “constant speed”?
11. A force of 40.0 n is required to start a 5.0 kg box moving across a horizontal
concrete floor. What is the coefficient of static friction between the box and
the floor?
12. If the 40.0 n force from problem 11 continues, the box accelerates at 0.70 m/s2.
What is the coefficient of sliding friction?
[0.74]
[144 n]
[0.82]