The position $x$ of a particle moving along $x$-axis at time $(t)$ is given by the equation $t=\sqrt{x}+2$, where $x$ is in metres and $t$ in seconds. the work done by the force in first four seconds is .............. $J$

A small steel sphere of mass $m$ is falling vertically through a viscous liquid with a constant speed $v$ . Which row in the table correctly describes the changes with time in the kinetic energy and gravitational potential energy of the sphere?

Kinetic Energy || Gravitational Potential Energy

A ball of mass $0.2\ kg$ is thrown vertically upwards by applying a force by hand. If the hand moves $0.2\ m$ while applying the force and the ball goes upto $2\ m$ height further, find the  magnitude of the force .......... $N$ .(consider $g = 10\; m/s^2$)

An engine is attached to a wagon through a shock absorber of length $1.5\, {m}$. The system with a total mass of $40,000\, {kg}$ is moving with a speed of $72\, {kmh}^{-1}$ when the brakes are applied to bring it to rest. In the process of the system being brought to rest, the spring of the shock absorber gets compressed by $1.0\, {m}$. If $90\, \%$ of energy of the wagon is lost due to friction, the spring constant is $....\, \times 10^{5}\, {N} / {m}$

A knife of mass $m$ is at a height $x$ from a large wooden block. The knife is allowed to fall freely, strikes the block and comes to rest after penetrating distance $y$. The work done by the wooden block to stop the knife is ..............

What is exothermic reaction and endothermic reaction ?