Question

A man pushes on a piano of mass 180 kg so that it slides at a constant velocity of 12.0 cm/s down a ramp that is inclined at 11.0degrees above the horizontal. No appreciable friction is acting on the piano. Calculate the magnitude and direction of this push

(a)if the man pushes parallel to the incline,
We take the upward direction to be positive and downward one to be negative. The sign of the force should be entered correctly.
(b)if the man pushes the piano up the plane instead, also at 12.0 cm/s parallel to the incline,
(c)if the man pushes horizontally, but still with a speed of 12.0 cm/s.

Answer 1

weight has a downward component;
weight in negative direction mg*CosTheta

a) going down the plane, without friction, the man would have to chaase the piano to push it. Have you ever chased a sled on a icy hill?

b) pushing up> Push=frition=mgSinTheta

c) horizontal? then his push in the up direction is push*cosTheta=mg*sinTheta

Answer 2

Bobpursley,

That doesnt answer the question for c???