Two bodies $A$ and $B$ of masses $20 \ kg$ and $5 \ kg$ respectively are at rest. Due to the action of a force of $40 \ N$ separately,if the two bodies acquire equal kinetic energies in times $t_A$ and $t_B$ respectively,then $t_A: t_B=$

$A$ truck and a car are moving with equal velocity. On applying the brakes,both will stop after a certain distance. Which of the following is true?

$A$ bullet of mass $10 \,g$ is fired horizontally with a velocity $1000 \,ms^{-1}$ from a rifle situated at a height $50 \,m$ above the ground. If the bullet reaches the ground with a velocity $500 \,ms^{-1}$, the work done against air resistance in the trajectory of the bullet is : $(g=10 \,ms^{-2})$ (in $\,J$)

$A$ spherical bowl of radius $R = 2 \ m$ is placed on a horizontal plane. $A$ particle of mass $m = 1 \ g$ oscillates on its inner surface. If the particle starts from a point on the bowl at a height of $h = 1 \ cm$ from the horizontal plane and the coefficient of friction is $\mu = 0.01$,find the total distance $s$ traveled by the particle before it comes to rest at the bottom of the bowl. (in $m$)

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

The inclined surfaces of two movable wedges of same mass $M$ are smoothly conjugated with the horizontal plane as shown in the figure. $A$ washer of mass $m$ slides down the left wedge from a height $h$. To what maximum height will the washer rise along the right wedge? Neglect friction.