The position of a particle moving on a straight line under the action of a force is given as $x=50t-5t^2.$ Here, $x$ is in metre and $t$ is in second. If mass of the particle is $2 \mathrm{kg}$, the work done by the force acting on the particle in first $5 \mathrm{s}$ is

A rectangular block is moving along a frictionless path, when it encounters the circular loop as shown. The block passes points $1,2,3,4,1$ before returning to the horizontal tracks. At point $3$

Figure shows a body $A$ at the top of a frictionless hemispherical inverted bowl of radius $R.$ If the body starts slipping from the highest point, then the horizontal distance between the point where it leaves contact with sphere and the point at which the body was placed is