A body of mass M hits normally a rigid wall with velocity v and bounces back with the same velocity. The impulse experienced by the body is

(1) 1.5 Mv                                                 

(2) 2 Mv

(3) zero                                                     

(4) Mv

A gramophone record is revolving with an angular velocity $\omega .$ A coin is placed at a distance r from the centre of the record. The static coefficient of friction is $\mu .$ The coin will revolve with the record if: 

1. $r=\mu g{\omega }^2$                                       2. $r<\frac{{\omega }^2}{\mu g}$

3. $r\le \frac{\mu g}{{\omega }^2}$                                         4. $r\ge \frac{\mu g}{{\omega }^2}$

The mass of a lift is 2000 kg. When the tension in the supporting cable is 28000 N, its acceleration is:

(a) $30 {\mathrm{ms}}^{-2} \mathrm{downwards}$                                      (b) $4 {\mathrm{ms}}^{-2} \mathrm{upwards}$

(c) $4 {\mathrm{ms}}^{-2} \mathrm{downwards}$                                        (d) $14 {\mathrm{ms}}^{-2} \mathrm{upwards}$

Three forces acting on a body are shown in the figure. To have the resultant force only along the y-direction, the magnitude of the minimum additional force needed is 

(a) 0.5N

(b) 1.5N

(c) $\frac{\sqrt{3}}{4}$ N

(d) $\sqrt{3}$N

A particle of mass m is projected with velocity v making an angle of ${45}^{°}$ with the horizontal. When the particle lands on the level ground the magnitude of the change in its momentum will be 

1.  2mv

2. mv/$\sqrt{2}$

3. mv$\sqrt{2}$

4. zero 

Sand is being dropped on a conveyor belt at the rate of M kg/s. The force necessary to keep the belt moving with a constant velocity of v m/s will be 

1. Mv newton 

2. 2Mv newton 

3. $\frac{Mv}{2}$newton 

4. zero

A person of mass 60 kg is inside a lift of mass 940 kg and presses the button on control panel. The lift starts moving upwards with an acceleration $1.0$ $\mathrm{m}/{\mathrm{s}}^2$. If $\mathrm{g}=10$ $\mathrm{m}/{\mathrm{s}}^2$, the tension in the supporting cable is:

1. 9680 N

2. 11000 N

3. 1200 N

4. 8600 N

A car of mass m is moving on a level circular track of radius R. If ${\mathrm{\mu }}_{\mathrm{s}}$ represent the static friction between the road and tyres of the car, then the maximum speed of the car in circular motion is given by:

A balloon with mass m is descending down with an acceleration a (where a < g). How much mass should be removed from it so that it starts moving up with an acceleration a?

1. 2ma/g+a

2. 2ma/g-a

3. ma/g+a

4. ma/g-a

Two stones of masses m and 2m are whirled in horizontal circles, the heavier one in a radius r/2 and the lighter one in radius r. The tangential speed of lighter stone is n times that of the value of heavier stone when they experience same centripetal forces. The value of n is

1. 2

2. 3

3. 4

4. 1