A block of weight w = 30.0 N sits on a frictionless inclined plane, which makes

Question

A block of weight w = 30.0 N sits on a frictionless inclined plane, which makes an angle = 28.0 with respect to the horizontal, as shown in the figure. A force of magnitude F = 14.1 N , applied parallel to the incline, is just sufficient to pull the block up the plane at constant speed.

-The block moves up an incline with constant speed. What is the total work Wtotal done on the block by all forces as the block moves a distance L = 3.00 m up the incline? Include only the work done after the block has started moving at constant speed, not the work needed to start the block moving from rest.

-What is Wg, the work done on the block by the force of gravity w  as the block moves a distance L = 3.00 m up the incline?

Explanation / Answer

Given

   block of weight W = 30.0 N, on a frictionless inclined plane with inclination theta = 28 degrees

applied force magnitude F = 14.1 N parallel to the incline , due to which it moved up a distance of s = 3 m

and the block moving up with constant speed.

a)

Total Work done by all the forces is Wt = 0 J

because the block is moving with constant speed , and from work energy theorem the total work done by a force on the object is equal to the change in kinetic energy

there is no change in speed ===> no change in k.e ===> WT = 0 J

b)

   Work done by the force of gravity on the block is

   Wg = Fy*s

   Wg = - mg sin theta *s

   = -30*sin28*3 J

   = - 42.252 J

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