An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass 1 kg moves with a speed of 12 ms^-1 and the second part of mass 2kg moves with 8 ms^-1 speed. If the third part flies off with 4 ms^-1 speed, then its mass is

1. 3kg
 

2. 5kg
 

3. 7kg
 

4. 17kg

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
\(1.~2mgR\)
\(2.~\frac{2}{3}mgR\)
\(3.~3mgR\)
\(4.~\frac{1}{3}mgR\)




 

Two spheres A and B of masses $m_1 and m_2$ respectively collide. A is at rest initially and B is moving with velocity v along x-axis. After collision B has a velocity $\frac{v}{2}$ in a direction perpendicular to the original direction.The mass A moves after collision in the direction

1. same as that of B

2. opposite to that of B

3. $\theta ={\tan }^{-1}\left(\frac{1}{2}\right)to the x‐axis$

4.$\mathrm{ \theta }={\tan }^{-1}\left(\frac{-1}{2}\right)to the x‐axis$

magnitude \(P_0\). The instantaneous velocity of this car is proportional to:
1. \(t^2 P_0\)
2. \(t^{\frac{1}{2}}\)
3. \(t^{\frac{-1}{2}}\)
4. \(\frac{t}{\sqrt{m}}\)

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

Force F on a particle moving in a straight line varies with distance d as shown in the figure. The work done on the particle during its displacement of 12 m is

(a) 21 J                                                  (b) 26 J

(c) 13 J                                                   (d) 18 J

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. $\frac{1}{2}\frac{{\mathrm{Mv}}^2}{\mathrm{T}}$

An explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are, 1 kg first part moving with a velocity of $12 {\mathrm{ms}}^{-1}$ and 2 kg second part moving with a velocity of $8 {\mathrm{ms}}^{-1}.$ If the third part flies off with a velocity of $4 {\mathrm{ms}}^{-1},$ its mass would be 

1. $5 \mathrm{kg}$                                          
2. $7 \mathrm{kg}$
3. $17 \mathrm{kg}$                                         
4. $3 \mathrm{kg}$

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? $\left(\mathrm{g}=10 {\mathrm{ms}}^{-2}\right)$

1. 20 J                               
2. 30 J
3. 40 J                               
4. 10 J