Question

A block of mass 1 kg is placed at point A of a rough track shown in figure (8-E6). If slightly pushed towards right, it stops at point B of the track. Calculate the work done by the frictional force on the block during its transit from A to B.
Figure

Answer 1

The work done by the frictional force on the block during its transit from A to B is - 2 Joule

Explanation:

given values in the question  

block’s mass = 1 kg.

H = 1 meter

h = 0.8 meter

Now the block gets down = H - h = 1.0 - 0.8  

h=0.2 m  (from A to B)

Lost potential energy in the process = mgh

= 1 × 10 × 0.2

Potential energy which lost in this process = 8 J

If there is no frictional force that will turn the Potential Energy into Kinetic Energy.  

When the block terminates at point B. Since the negative work done through frictional force is similar to potential energy lost in the process.

= -2 J.

Thus the block's frictional force during its transit is -2 J.

Answer 2

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A to B -2 joule