Force acting on a particle is $F=3i-2j+4k$ and its displacement is given by $AB=(2,-1,0)$, then the work done is _____.

Assertion $\left(A\right)$ : The work done by the electrostatic force is zero when a point charge moves in a circular path around another charge.

Reason $\left(R\right)$ : The dot product of force and displacement vectors gives work done.

The diagram shows a barrel of weight $1.0\times {10}^3 \mathrm{N}$ on a frictionless slope inclined at $30°$ to the horizontal.

The force is parallel to the slope. Whet is the work done in moving the barrel a distance of $5.0 \mathrm{m}$ up the slope?

A lawn roller has been pushed through a distance of $80 \mathrm{m}$ by applying a force of $50 \mathrm{kg}.$wt in a direction inclined at $60°$ with the ground. Calculate the work done on the roller.

A block of mass $m$ slides from rest at a height $H$ on a frictionless inclined plane as shown in the figure. It travels a distance $d$ across a rough horizontal surface with coefficient of kinetic friction $\mu$ and compresses a spring of spring constant $k$ by a distance $x$  before coming to rest momentarily. Then the spring extends and the block travels back attaining a final height of $h$.

Then