A boy pulls on a 25-kg sled at an upward angle of 20° (above
horizontal). The coefficients of static friction and kinetic
friction of wood on snow are 0.14 and 0.1, respectively.
a) Calculate the minimum force he must exert to get the sled
moving.
b) Assume that the boy continues to pull after the sled begins
to move (same force as in part a). What is the acceleration of the
sled after it begins to move?
c) What pulling force is needed to keep the sled moving at a
constant velocity?
d) What is the acceleration of the sled once the boy lets go of
it?