The work-energy theorem is valid in the presence of:

$A$ body of mass $3 \text{ kg}$ is moving under the action of a force which causes a displacement of $\left(\frac{t^3}{3}\right) \text{ m}$, where '$t$' is time in seconds. The work done by the force in the first $2 \text{ seconds}$ is: (in $\text{ J}$)

Write the equation of total mechanical energy of a body of mass $m$ falling freely from a height $H$.

$A$ ball bounces to $80\%$ of its original height. What fraction of its mechanical energy is lost in each bounce?

$A$ uniform flexible chain of mass $m$ and length $2l$ hangs in equilibrium over a smooth horizontal pin of negligible diameter. What will be the speed of the chain when it leaves the pin?

What does the law of conservation of energy state?