Work Energy Theorem

Q. A ball is placed on a compressed spring. What form of energy does the spring possess? On releasing the spring, the ball flies away. Give a reason. $\left[3\text{marks}\right]$

Q. A block of mass 15 kg moving along x direction at a constant speed of 20${ms}^{-1}.$ It is subjected to a retarding force $F=2xJ{m}^{-1}$ during its journey from $x=10$ m to $x=40m.$ Its final kinetic energy will be:

1. 500 J
2. 1000 J
3. 1500 J
4. 2000 J

Q. The curved portions are smooth and horizontal surface is rough. The block is released from $P$. At what distance from $A$ it will stop (if $\mu =0.2$)

Q. Work done in time $t$ on a body of mass $m$ which is accelerated from rest to speed $v$ in time $t_1$ as a function of time $t$ is given as

1. $\frac{1}{2}m\frac{v^2}{t_1^2}{t}^2$
2. $\frac{1}{2}{\left(\frac{mv}{t_1}\right)}^2{t}^2$
3. $m\frac{v}{t_1}{t}^2$
4. $\frac{1}{2}m\frac{v}{t_1}{t}^2$

Q. The power supplied by a force acting on a particle moving in a straight line is constant . The velocity of the particle varies with the displacement $x$ as

1. $x^{1/2}$
2. $x^{1/3}$
3. $x$
4. $x^2$

Q. A ball is thrown vertically upward with a velocity of $20\text{m}$/s. At what height will its potential and kinetic energies be equal?
$g=10{\text{m/s}}^2$

1. $12\text{m}$
2. $20\text{m}$
3. $15\text{m}$
4. $10\text{m}$

Q. On what does the escape velocity of a moon depend?
I. Mass of celestial body.
II. The distance from the centre of mass to the escaping object.

1. Only I
2. Only II
3. Both I and II
4. Neither I nor II