A block rests on an inclined plane with enough friction to prevent it from sliding down. To start the block moving, is it easier to push it up the plane or down the plane? Why?
Solution 10DQ For an object of mass m close to the surface of the earth, gravity acts in a downward direction (toward the center of the earth) and has magnitude mg , regardless of the presence or absence of other forces and regardless of the object's motion, velocity, or acceleration. Gravity acts on the block with the same magnitude and direction regardless of whether the block is sliding up, sliding down, or remaining where it is. Thus, the analysis of the gravitational force and its components is completely universal.It is easier to push down because acceleration will be acting same direction. The gravitational force component is mg sin. The magnitude and direction of the friction force are not clear. We have three cases, the case of no sliding, where an upward static friction f acts (subject to the constraint f N the case of sliding down, s s s where an upward kinetic friction f = N acts, and the case of s liding up, where a k k downward kinetic friction f = N acts. k k Or g sin-mg cos down g sin+mg cos up
