Three blocks with masses m, 2m, and 3m are connected by strings as shown in the figure. After an upward force F is applied on block m, the masses move upward at constant speed v. What is the net force on the block of mass 2m? (g is the acceleration due to gravity). 

        

1. 2mg
2. 3mg
3. 6mg
4. zero

A car of mass 1000 kg negotiates a banked curve of radius 90 m on a frictionless road. If the banking angle is 45^o, the speed of the car is:

1. 20 ms^-1

2. 30 ms^-1

3. 5 ms^-1

4. 10 ms^-1

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.  1.5Mv

2.  2Mv

3.  zero

4.  Mv

A block of mass m is in contact with the cart C as shown in the figure. 
        
The coefficient of static friction between the block and the cart is $\mathrm{\mu }$. The acceleration $\mathrm{\alpha }$ of the cart that will prevent the block from falling satisfies:

1. $\mathrm{\alpha }>\frac{\mathrm{mg}}{\mathrm{\mu }}$

2. $\mathrm{\alpha }>\frac{\mathrm{g}}{\mathrm{\mu m}}$

3. $\mathrm{\alpha }\ge \frac{\mathrm{g}}{\mathrm{\mu }}$

4. $\mathrm{\alpha }<\frac{\mathrm{g}}{\mathrm{\mu }}$

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. $r\ge \frac{\mu g}{{\omega }^2}$

An explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are, the first part 1 kg moving with a velocity of 12 ${\mathrm{ms}}^{-1}$ and the second part 2 kg 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 kg
2. 7 kg
3. 17 kg
4. 3 kg

A body, under the action of a force $\overrightarrow{\mathrm{F}}=6\hat{i}-8\hat{j}+10\hat{k}$, acquires an acceleration of 1 ms^-2. The mass of this body must be:

1. 2 √10 kg

2. 10 kg

3. 20 kg

4. 10 √2 kg