What is the work done by a coolie walking on a horizontal platform with a load on his head?

$A$ man rowing a boat upstream is at rest with respect to the shore. Is he doing work?

$(a)$ State the law of conservation of energy.
$(b)$ What is the work done to increase the velocity of a car from $36 \, km/h$ to $72 \, km/h$ if the mass of the car is $1500 \, kg$? Does the work done by the force have a negative or a positive magnitude?
$(c)$ Where does an oscillating pendulum have maximum potential energy $(PE)$ and kinetic energy $(KE)$?

Define potential energy. Write an expression for potential energy. Write the $SI$ unit of potential energy.

$A$ force of $10\, N$ moves a body with a constant speed of $2\, m s^{-1}$. Calculate the power of the body.

Give the formula for calculating work done. What is the $SI$ unit of work?