Q. No.A bullet hits a block kept at rest on a smooth horizontal surface and gets embedded into it. Which of the following does not change?
1.
linear momentum of the block
2.
kinetic energy of the block
3.
gravitational potential energy of the block
4.
temperature of the block
A block of mass \(m\) is being lowered by means of a string attached to it. The system moves down with a constant velocity. Then:
| 1. | the work done by gravity on the block is positive. |
| 2. | the work done by force, \(F \) (the force of the string) on the block is negative. |
| 3. | the work done by gravity is equal in magnitude to that done by the string. |
| 4. | All of the above are true. |
The total work done on a particle is equal to the change in its kinetic energy:
| 1. | always |
| 2. | only if the forces acting on it are conservative |
| 3. | only if gravitational force alone acts on it |
| 4. | only if elastic force alone acts on it |
__________ of a two-particle system depends only on the separation between the two particles. The most appropriate choice for the blank space in the above sentence is:
1. kinetic energy
2. total mechanical energy
3. potential energy
4. total energy
| 1. | \(\dfrac{m'}{m}=\dfrac{1}{10}\) | 2. | \(\dfrac{m'}{m}=\dfrac{1}{9}\) |
| 3. | \(\dfrac{m'}{m}=\dfrac{1}{8}\) | 4. | \(\dfrac{m'}{m}=\dfrac{1}{2}\) |
A rod of mass \(M\) and length \(L\) is suspended vertically at its highest point. The rod is held such that it is horizontal and free to rotate about \(A\) and then released. There is no friction anywhere.
The kinetic energy of the rod, when it reaches the lowest position is:
| 1. | \(MgL\) | 2. | \(\dfrac{MgL}{2}\) |
| 3. | \(\dfrac{2}{3}MgL\) | 4. | \(\dfrac{MgL}{12}\) |
Then:
1. \(\dfrac{W_F}{M}=\dfrac{W_m}{m}\)
2. \(W_F\cdot M=W_m\cdot m\)
3. \(\dfrac{W_F}{M+m}=\dfrac{W_m}{m}\)
4. \(\dfrac{W_F}{M}=\dfrac{W_m}{m+M}\)
| 1. | \(\frac12mu^2=\frac12kx^2\) | 2. | \(\frac12mu^2cos^2\theta=\frac12kx^2\) |
| 3. | \(\frac12mu^2=\frac12kx^2cos^2\theta\) | 4. | \(\frac12mu^2sin^2\theta=\frac12kx^2\) |
Water falls from a height of 60 m at the rate of 15 kg/s to operate a turbine. The losses due to frictional force are 10% of the input energy. How much power is generated by the turbine?
| 1. | 12.3 kW | 2. | 7.0 kW |
| 3. | 10.2 kW | 4. | 8.1 kW |
(Take \(g=10\) ms–2)
1. \(23500\)
2. \(23000\)
3. \(20000\)
4. \(34500\)
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