If an electric iron of $1200 \, W$ is used for $30$ minutes everyday, find the electric energy consumed in the month of April. (in $kWh$)

$(a)$ 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 $v$.

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 $N$)?

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

State the relation between $kWh$ and joule. Define $1$ watt.

State the type of energy transformation in the following cases: $(a)$ in a loudspeaker $(b)$ solar battery.