How much work does a pulling force of $40\, N$ do on a $20\, kg$ box in pulling it $8\, m$ across a smooth floor at a constant speed? The pulling force is directed at $60^{\circ}$ above the horizontal. (Answer in $J$)

The kinetic energy $K$ of a particle moving in a straight line depends upon the distance $s$ as $K = as^2$. The force acting on the particle is

$A$ porter lifts a heavy suitcase of mass $80\, \text{kg}$ and at the destination lowers it down by a distance of $80\, \text{cm}$ with a constant velocity. Calculate the work done by the porter in lowering the suitcase. (Take $g = 9.8\, \text{m/s}^2$) (In $\text{J}$)

$A$ force $\vec{F} = -5 \hat{i} - 7 \hat{j} + 3 \hat{k}$ acting on a particle causes a displacement $\vec{s} = 3 \hat{i} - 2 \hat{j} + a \hat{k}$. If the work done is $14 \ J$,then the value of '$a$' is:

If $\vec{F}$ and $\vec{S}$ are force and displacement respectively,and the work done by them is zero,then:

$A$ force $F = (5\hat{i} + 3\hat{j}) \ N$ acts on an object,causing a displacement of $r = (2\hat{i} - 1\hat{j}) \ m$. Calculate the work done in $J$.