$300$ Joule of work is done in sliding up a $2 \,kg$ block on an inclined plane to a height of $10\, metres$. Taking value of acceleration due to gravity $‘g’ $ to be $10 \,m/s^2$, work done against friction is ........ $J$

A body dropped from height $‘H’$ reaches the ground with a speed of $1.1 \sqrt {gH}$ . Calculate the work done by air friction? .............. $\mathrm{mgH}$

A number of identical cubical blocks of edge $'a'$ and mass $m$ are lying on a horizontal table. The work done on the blocks in arranging them in a column of height $(n + 1)a$ on the table is

Explain the different forms of energy.

$(a)$ Heat Energy

$(b)$ Chemical Energy

$(c)$ Electrical Energy

Two inclined planes are placed as shown in figure.

A block is projected from the Point $A$ of inclined plane $A B$ along its surface with a velocity just sufficient to carry it to the top Point $B$ at a height $10 m$. After reaching the Point $B$ the block slides down on inclined plane $BC$. Time it takes to reach to the point $C$ from point $A$ is $t (\sqrt{2}+1) s$. The value of $t$ is........(use $g =10 m / s ^{2}$ )

If $250 \,J$ of work is done in sliding a $5 \,kg$ block up an inclined plane of height $4 \,m$. value of Work done against friction is ............. $J$ $\left(g=10 \,ms ^{-2}\right)$