Question

A body of mass m is moving with a uniform velocity u. A force is applied to the body due to which its velocity increases from u to v. How much work is being done by the force?

Answer 1

Work done by all the forces equals change in kinetic energy for a free body

mass = m kg

Initial velocity = u

Final velocity = v

Initial Kinetic energy, $K_i=\frac{1}{2}m{u}^2$

Final Kinetic energy, $K_f=\frac{1}{2}m{v}^2$

Work done, $W=\Delta K=K_f-K_i=\frac{1}{2}m{v}^2-\frac{1}{2}m{u}^2=\frac{1}{2}m(v^2-u^2)$