When an object is dragged $10 \, m$ along a road,a frictional force of $200 \, N$ acts in the direction opposite to its motion. What is the work done by the frictional force on the object (in $, J$)?

When a particle moves from its origin to a point with position vector $\vec{r} = (2\hat{i} - \hat{j}) \ m$,it is subjected to a force $\vec{F} = (5\hat{i} + 3\hat{j} + 2\hat{k}) \ N$. What is the work done by the force in Joules?

When a force of $50 \, N$ is applied to an object,it undergoes a displacement of $10 \, m$ at an angle of $60^\circ$ with the direction of the force. The work done is ......... $J$.

The work done in pulling up a block of wood weighing $2 \, kN$ for a length of $10 \, m$ on a smooth plane inclined at an angle of $15^\circ$ with the horizontal is ............. $kJ$.

$A$ body of mass $m$ is moving in a circle of radius $r$ with a constant speed $u$. The force on the body is $mv^2/r$ and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle?

$A$ block of mass $m$ is kept in an elevator which starts moving downward with an acceleration $a$ as shown in the figure. The block is observed by two observers $A$ and $B$ for a time interval $t_0$. According to observer $B$,the net work done on the block is