Q. No.Choose the incorrect alternative:
| 1. | Newton's first law is the law of inertia. |
| 2. | Newton's first law states that if the net force on a system is zero, the acceleration of any particle of the system is not zero. |
| 3. | Action and reaction act simultaneously. |
| 4. | The area under the force-time graph is equal to the change in momentum. |
Three blocks with masses of \(m\), \(2m\), 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 a 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 |
| Assertion (A): | A standing bus suddenly accelerates. If there was no friction between the feet of a passenger and the floor of the bus, the passenger would move back. |
| Reason (R): | In the absence of friction, the floor of the bus would slip forward under the feet of the passenger. |
| 1. | (A) is True but (R) is False. |
| 2. | (A) is False but (R) is True. |
| 3. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 4. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
A body is moving with a velocity of \(2\hat i\) m/s. If the force acting on the body is \((2\hat i+3\hat j+3\hat k)\) N, then the momentum of the body is changing in:
1. \(X\)-direction only
2. \(X\text-Y\) directions
3. \(Y\text-Z\) directions
4. In all \(X\text-Y\text-Z\) directions
| 1. | along south-west | 2. | along eastward |
| 3. | along northward | 4. | along north-east |
| 1. | \(2~\text{kg}\) | 2. | \(3~\text{kg}\) |
| 3. | \(4~\text{kg}\) | 4. | \(5~\text{kg}\) |
A particle moves in the \(XY\text-\)plane under the action of a force \(F\) such that the components of its linear momentum \(p\) at any time \(t\) are \(p_x = 2 \cos t\), \(p_y = 2 \sin t\). The angle between \(F\) and \(p\) at time \(t\) will be:
| 1. | \(90^{\circ}\) | 2. | \(0^{\circ}\) |
| 3. | \(180^{\circ}\) | 4. | \(30^{\circ}\) |
A lift is going up. The total mass of lift and the passenger is \(1500\) kg. The variation in the speed of the lift is as given in the graph. The tension in the rope pulling the lift at \(t=11^{\text{th}}\) s will be:
1. \(17400\) N
2. \(14700\) N
3. \(12000\) N
4. zero
The variation of momentum with the time of one of the bodies in a two-body collision is shown in fig. The instantaneous force is the maximum corresponding to the point:
1. \(P\)
2. \(Q\)
3. \(R\)
4. \(S\)
At a wall, \(N\) bullets, each of mass \(m\), are fired with a velocity \(v\) at the rate of \(n\) bullets/sec upon the wall. The bullets are stopped by the wall. The reaction offered by the wall to the bullets is:
1. \(\frac{Nmv}{n}\)
2. \(nNmv\)
3. \(n\frac{Nv}{m}\)
4. \(nmv\)
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