The use of force to move an object is called work. This only applies if the object moves.
<span>The answer is a heterogeneous mixture. Mixtures can be homogeneous and heterogeneous. If a solid and a liquid of a mixture cannot be separated and the difference between them is not visible, it is called homogeneous mixture (or solution). If a solid and a liquid of a mixture are visible and can be separated easily, the mixture is called heterogeneous.</span>
Answer:
(A) 60 J
Explanation:
At state 1
KE₁=100 J
At state 2
KE₂ = 0
U₂=80 J
Given that surface is rough so friction force will act in opposite to the direction of motion
Lets take work done by friction = Wfr
From work power energy
Work done by all forces = Change in kinetic energy
Wfr + U₂=ΔKE
Wfr+80 = 100
Wfr= 20 J
Now when book slides from top position then
Wfr+ U = KEf - KEi
-20 + 80 = KEf-0
KEf= 60 J
(A) 60 J