$A$ body of mass $50 \ kg$ is lifted to a height of $20 \ m$ from the ground in two different ways as shown in the figure. The ratio of work done against gravity in both the respective cases will be:

$A$ particle moves from a point $(-2\hat i + 5\hat j) \ m$ to $(4\hat j + 3\hat k) \ m$ when a force of $(4\hat i + 3\hat j) \ N$ is applied. How much work has been done by the force? $J$

Under what condition is a force considered constant when it causes displacement?

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

$A$ block of mass $m$,kept on a horizontal surface,is moved through a distance $s$ by applying a horizontal force $F$ to it. What is the work done by the normal reaction?

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.