$A$ uniform force of $(3\hat i + \hat j) \text{ N}$ acts on a particle of mass $2 \text{ kg}$. The particle is displaced from position $(2\hat i + \hat k) \text{ m}$ to position $(4\hat i + 3\hat j - \hat k) \text{ m}$. The work done by the force on the particle is ............. $J$.

An adult weighing $600 \, N$ raises the centre of gravity of his body by $0.25 \, m$ while taking each step of $1 \, m$ length in jogging. If he jogs for $6 \, km$,calculate the energy utilised by him in jogging assuming that there is no energy loss due to friction of ground and air. Assuming that the body of the adult is capable of converting $10 \, \%$ of energy intake in the form of food,calculate the energy equivalents of food that would be required to compensate for the energy utilised for jogging.

When is the work done by a force positive and when is it negative?

$A$ particle is moved from $(0, 0)$ to $(a, a)$ under a force $\vec{F} = (3\hat{i} + 4\hat{j})$ through two paths. Path $1$ is $OP$ and path $2$ is $OQP$. Let $W_1$ and $W_2$ be the work done by this force in these two paths respectively. Then

$A$ rope is used to lower a block of mass $M$ vertically downwards by a distance $x$ with a constant downward acceleration of $g/2$. What is the work done by the rope on the block?

Write the definition of work and kinetic energy.