Horizontal Friction #2
Name:________________________
42.
(II) A box is given a push so that it slides across the floor. How far will it go, given that
the coefficient of kinetic friction is 0.15 and the push imparts an initial speed of 3.5 m/s?
43.
(II) A 1280-kg car pulls a 350-kg trailer. The car exerts a horizontal force of 3.6 × 103 N
against the ground in order to accelerate. What force does the car exert on the trailer?
Assume an effective friction coefficient of 0.15 for the trailer.
44.
(II) Police investigators, examining the scene of an accident involving two cars, measure
72-m-long skid marks of one of the cars, which nearly came to a stop before colliding.
The coefficient of kinetic friction between rubber and the pavement is about 0.80.
Estimate the initial speed of that car assuming a level road.
Horizontal Friction #2
Name:________________________
45.
(II) Drag-race tires in contact with an asphalt surface have a very high coefficient of
static friction. Assuming a constant acceleration and no slipping of tires, estimate the
coefficient of static friction needed for a drag racer to cover 1.0 km in 12 s, starting from
rest.
46.
(II) For the system of Fig. 4–32 (Example 4–20), how large a mass would box A have to
have to prevent any motion from occurring? Assume  s = 0.30.
47.
(II) In Fig. 4–56 the coefficient of static friction between mass mA and the table is 0.40,
whereas the coefficient of kinetic friction is 0.20. (a) What minimum value of mA will
keep the system from starting to move? (b) What value(s) of mA will keep the system
moving at constant speed? [Ignore masses of the cord and the (frictionless) pulley.]