Work, Energy and Power

In elastic collision

• both momentum and kinetic energies are conserved

• both momentum and kinetic energies are not conserved

• only energy is conserved

• only mechanical energy is conserved

A body rolls down an inclined plane. If its kinetic energy of rotation is 40% of its kinetic energy of translation, then the body is

• solid cylinder

• solid sphere

• disc

• ring

Force required to move a mass of 1 kg at rest on a horizontal rough plane (µ = 0.1 and g =9.8 ms^-2) is 

• 0.98 N

• 0.49 N

• 9.8 N

• 4.9 N

A body of mass 3 kg acted upon by a constant force is displaced by S' metre, given by relation $\mathrm{S} = \frac{1}{3} {\mathrm{t}}^2$, where t is in second. Work done by the force in 2 is

• $\frac{8}{3} \mathrm{J}$

• $\frac{19}{5} \mathrm{J}$

• $\frac{5}{19} \mathrm{J}$

• $\frac{3}{8} \mathrm{J}$

Two particles have masses m and 4m and their kinetic energies are in the ratio 2 : 1. What is the ratio of their linear momenta ?

• $\frac{1}{\sqrt{2}}$

• $\frac{1}{2}$

• $\frac{1}{4}$

• $\frac{1}{16}$

The force F acting on a particle moving in a straight line is shown below. What is the work done by the force on the particle in the 1st metre of the trajectory ?

• 5 J

• 10 J

• 15 J

• 2.5 J

If the kinetic energy of a body changes by 20 %, then its momentum would change by

• 20 %

• 24 %

• 9.5 %

• 44 %

The work done in carrying a charge Q once around a circle of radius r about a charge q at the centre is

• $\frac{\mathrm{qQ}}{4{\mathrm{\pi \epsilon }}_0\mathrm{r}}$

• $\frac{\mathrm{qQ}}{4{\mathrm{\pi \epsilon }}_0} \frac{1}{\mathrm{\pi r}}$

• $\frac{\mathrm{qQ}}{4{\mathrm{\pi \epsilon }}_0} \left(\frac{1}{2\mathrm{\pi r}}\right)$

• Zero

The displacement x of a particle at time t moving under a constant force is t = $\sqrt{\mathrm{x}}$ + 3, x in metre, t in second. Find the work done by the interval from t = 0 to t= 6 s.

Two blocks of 2 kg and 1 kg are in contact on a frictionless table. If a force of 3 N is applied on 2 kg block, then the force of contact between the two blocks will be

• zero

• 1 N

• 2 N

• 3 N