A body of mass m is taken from the earth’s surface to the height equal to twice the radius (R) of the earth. The change in potential energy of the body will be
\(1.~2mgR\)
\(2.~\frac{2}{3}mgR\)
\(3.~3mgR\)
\(4.~\frac{1}{3}mgR\)




 

The potential energy of a particle in a force field is $U=\frac{A}{r^2}-\frac{B}{r},$where A and B are positive constants and r is the distance of particle from the centre of the field. For stable equilibrium, the distance of the particle is 

(1) B/2A                                     

(2)2A/B

(3)A/B                                       

(4)B/A

A car of mass m starts from rest and 

accelerates so that the instantaneous

power delivered to the car has a constant

magnitude ${\mathrm{P}}_0$. The instantaneous 

velocity of this car is proportional to

1. ${\mathrm{t}}^2{\mathrm{P}}_0$               2. ${\mathrm{t}}^{1/2}$

3. ${\mathrm{t}}^{-1/2}$              4. $\mathrm{t}/\sqrt{\mathrm{m}}$

The potential energy of a system increases if work is done

(1) by the system against a conservative force 

(2) by the system against a nonconservative force

(3) upon the system by a conservative force

(4) upon the system by a nonconservative force

A ball moving with velocity $2 m{s}^{-1}$ collides head on with another stationery ball of double the mass. If the coefficient of restitution is 0.5, then their velocities (in $m{s}^{-1}$) after collision will be 

(1)0,1                                               

(2)1,1

(3)1,0.5                                             

(4)0,2 

An engine pumps water through a hosepipe. Water passes through the pipe and leaves it with a velocity of 2 $m{s}^{-1}.$The mass per unit length of water in the pipe is 100 $kg{m}^{-1}.$What is the power of the engine?

1. 400 W                                       

2. 200 W

3. 100 W                                       

4. 800 W

A particle of mass M starting from rest undergoes uniform acceleration. If the speed acquired in time T is v, the power delivered to the particle is 

(1) $\frac{{\mathrm{Mv}}^2}{\mathrm{T}}$                                 

(2) $\frac{1}{2}\frac{{\mathrm{Mv}}^2}{{\mathrm{T}}^2}$

(3) $\frac{{\mathrm{Mv}}^2}{{\mathrm{T}}^2}$                                   

(4) $\frac{1}{2}\frac{{\mathrm{Mv}}^2}{\mathrm{T}}$

A body of mass 1 kg is thrown upwards with a velocity $20 {\mathrm{ms}}^{-1}.$ It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction? $\left(\mathrm{g}=10 {\mathrm{ms}}^{-2}\right)$

(a) 20 J                               (b) 30 J

(c) 40 J                                (d) 10 J

A block of mass M is attached to the lower end of a vertical spring. The spring is hung from the ceiling and has a force constant value of k. The mass is released from rest with the spring initially unstretched. The maximum extension produced along the length of the spring will be:

The points of maximum and minimum attraction in the curve between potential energy (U) and distance (r) of a diatomic molecules are respectively -

(1) S and R

(2) T and S

(3) R and S

(4) S and T