State whether the following statement is true or false:
In order to get minimum work,the angle between force and displacement should be $90^{\circ}$.

What is the work done by the force of gravity in the following cases?
$(a)$ $A$ satellite moving around the Earth in a circular orbit of radius $35000 \, km$.
$(b)$ $A$ stone of mass $250 \, g$ is thrown up to a height of $2.5 \, m$.

$A$ $2 \, m$ high person is holding a $25 \, kg$ trunk on his head and is standing at a roadways bus-terminus. How much work is done by the person (in $, J$)?

Which one of the following is not the unit of energy?

$(a)$ Give two conditions for work to be done.
$(b)$ What is the work done by frictional force on an object when dragged along a rough surface?
$(c)$ Relate power and work.
$(d)$ $A$ machine does $1960 \, J$ of work in $4 \, \text{minutes}$. What is the power?

State whether the following statement is true or false:
When velocity is halved,its kinetic energy becomes $\frac{1}{4}^{th}$ of its original value.