1. The choice of materials for an exciting playground slide should __________.
a. have a small coefficient of kinetic friction between cloth and the slide material
b. have a large coefficient of static friction between cloth and the slide material
c. have a small coefficient of static friction between cloth and the slide material
d. have a large coefficient of kinetic friction between cloth and the slide material
2. The coefficients of static and kinetic friction between the paper used in a cardboard box and a particular wooden floor are 0.5 and 0.3, respectively. Calculate the force that must be applied to slide a box with a weight of 40 N over the floor at a constant speed.
a. 40 N
b. 20 N
c. 12 N
d. 32 N
3. You press a book against a vertical wall. Express the force required to hold the book in place, F-applied, in terms of Wbook and μs.
a. F-applied=μkWbook
b. F-applied=μsWbook
c. F-applied=Wbook/μk
d. F-applied=Wbook/μs
4. Automobiles have anti-lock braking systems to prevent the wheels from locking when the brake is suddenly applied. Rather than applying a constant force on the wheel, an anti-lock braking system exerts a series of forces of short duration on the wheel. Why would this be true?
a. The static friction force is larger than the kinetic friction force
b. When the tire is locked, the frictional force is greater but the car cannot be steered
c. The coefficient of kinetic friction of the road in motion with respect the skidding tire is larger than the static coefficient of the road
d. The kinetic friction force is larger than the static friction force
Thanks in advance,
nadia :)
