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

An object of mass $1 \, kg$ has a potential energy of $1 \, J$ relative to the ground when it is at a height of: (in $, m$)

$A$ body is falling from a height $h$. After it has fallen a height $\frac{h}{2}$,it will possess

Four persons jointly lift a $250 \,kg$ box to a height of $1 \,m$ and hold it.
$(a)$ Calculate the work done by the persons in lifting the box.
$(b)$ How much work do they do just holding it?
$(c)$ Why do they get tired while holding it? $(g = 10 \,m/s^2)$

State whether the following statement is true or false:
If we know the speed and mass of an object,we can find out its kinetic energy.

$(a)$ Two bodies have equal masses and are moving with uniform velocities of $2\,v$ and $3\,v$. What is the ratio of their kinetic energies?
$(b)$ $A$ mass is dropped from height $h$. At halfway to the ground,what is the total energy?