$A$ light body and a heavy body have the same kinetic energy. Which one will have the greater momentum?

$(a)$ Define work done by a constant force on an object. Write an expression for the work done.
$(b)$ How much work will be done on an object by a force if the displacement of the object is zero?
$(c)$ What is the kinetic energy of an object? Write an expression for the kinetic energy of an object of mass $m$ moving with a speed $v$.

Mountain roads rarely go straight up but wind up gradually. Why?

$(i)$ State the law of conservation of energy.
$(ii)$ Show that the total mechanical energy of a freely falling body is conserved.

$(a)$ Can a body have energy without having momentum? Explain.
$(b)$ Can a body have momentum without having energy? Explain.

Define watt. Express kilowatt in terms of joule per second. $A$ $150 \, kg$ car engine develops $500 \, W$ for each $kg$. What force does it exert in moving the car at a speed of $20 \, m \, s^{-1}$ (in $N$)?