Question

A block of mass 1 kg is placed at a point A of a rough track shown in the figure . If slightly pushed towards the 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.

Answer 1

Given in the question :-
Mass of the block = 1 kg.
H = 1 m.
h = 0.8 m.
Now the block descends through = 1.0 -0.8 
h=0.2 m from A to B .
Lost P.E in the process = mgh
= 1 × 10 × 0.2
= 8 J
⇒If no frictional force is working so the Potential energy will be converted into Kinetic energy.
⇒When the block stops at point B. Since the negative W.D through frictional force is similar to potential energy lost in the process.
= -2 J.
Hence the frictional force on the block during it's transit is -2 J.


Hope it Helps.

Answer 2

heya friend!!☺☺
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heres your answer!!!☺☺

The block descends by 1.0 m - 0.8 m = 0.2 m in coming from A to B. Potential energy lost = mgh =1.0 x 10 x 0.2 J = 2.0 J
If there would not have been the frictional force, this lost P.E. would be converted to K.E. Since at point B the block stops, hence no K.E. at B. So, in this case, the negative work done by the frictional force is just equal to the P.E. lost i.e. = -2.0 J

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hope it helps you!!☺☺