Two similar springs \(P\) and \(Q\) have spring constants \(k_P\) and \(k_Q\), such that \(k_P>k_Q\). They are stretched, first by the same amount (case a), then by the same force (case b). The work done by the springs \(W_P\) and \(W_Q\) are related as, in case (a) and case (b), respectively:

1. \(W_P=W_Q;~W_P>W_Q\)
2. \(W_P=W_Q;~W_P=W_Q\)
3. \(W_P>W_Q;~W_P<W_Q\)
4. \(W_P<W_Q;~W_P<W_Q\)

Subtopic:  Elastic Potential Energy |
 74%
Level 2: 60%+
NEET - 2015
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A block of mass \(10\) kg, moving in the \(x\)-direction with a constant speed of \(10\) ms–1 is subjected to a retarding force \(F=0.1x\) J/m during its travel from \(x = 20\) m to \(30\) m. Its final kinetic energy will be:
1. \(475\) J 2. \(450\) J
3. \(275\) J 4. \(250\) J
Subtopic:  Work Energy Theorem |
 75%
Level 2: 60%+
NEET - 2015
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A particle of mass \(m\) is driven by a machine that delivers a constant power of \(k\) watts. If the particle starts from rest, the force on the particle at the time \(t\) is:
1. \( \sqrt{\frac{m k}{2}} t^{-1 / 2} \) 2. \( \sqrt{m k} t^{-1 / 2} \)
3. \( \sqrt{2 m k} t^{-1 / 2} \) 4. \( \frac{1}{2} \sqrt{m k} t^{-1 / 2}\)
Subtopic:  Power |
 55%
Level 3: 35%-60%
NEET - 2015
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Two particles of masses \(m_1\) and \(m_2\) move with initial velocities \(u_1\) and \(u_2\) respectively. On collision, one of the particles gets excited to a higher level, after absorbing energy \(E\). If the final velocities of particles are \(v_1\) and \(v_2\), then we must have:

1. \(m_1^2u_1+m_2^2u_2-E = m_1^2v_1+m_2^2v_2\)
2. \(\frac{1}{2}m_1u_1^2+\frac{1}{2}m_2u_2^2= \frac{1}{2}m_1v_1^2+\frac{1}{2}m_2v_2^2\)
3. \(\frac{1}{2}m_1u_1^2+\frac{1}{2}m_2u_2^2-E= \frac{1}{2}m_1v_1^2+\frac{1}{2}m_2v_2^2\)
4. \(\frac{1}{2}m_1^2u_1^2+\frac{1}{2}m_2^2u_2^2+E = \frac{1}{2}m_1^2v_1^2+\frac{1}{2}m_2^2v_2^2\)
Subtopic:  Collisions |
 62%
Level 2: 60%+
NEET - 2015
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On a frictionless surface, a block of mass \(M\) moving at speed \(v\) collides elastically with another block of the same mass \(M\) which is initially at rest. After the collision, the first block moves at an angle \(\theta\) to its initial direction and has a speed \(\frac{v}{3}\). The second block’s speed after the collision will be:

1. \(\frac{2\sqrt{2}}{3}v\) 2. \(\frac{3}{4}v\)
3. \(\frac{3}{\sqrt{2}}v\) 4. \(\frac{\sqrt{3}}{2}v\)
Subtopic:  Collisions |
 67%
Level 2: 60%+
NEET - 2015
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A body of mass (\(4m\)) is lying in the x-y plane at rest. It suddenly explodes into three pieces. Two pieces, each of mass (\(m\)) move perpendicular to each other with equal speeds (\(u\)). The total kinetic energy generated due to explosion is:

1. \(mu^2\) 2. \(1.5~mu^2\)
3. \(2~mu^2\) 4. \(3~mu^2\)

Subtopic:  Collisions |
 63%
Level 2: 60%+
AIPMT - 2014
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A uniform force of \((3 \hat{i} + \hat{j})\) newton acts on a particle of mass \(2~\text{kg}.\) Hence the particle is displaced from the position \((2 \hat{i} + \hat{k})\) metre to the position \((4 \hat{i} + 3 \hat{j} - \hat{k})\) metre. The work done by the force on the particle is:
1. \(6~\text{J}\)
2. \(13~\text{J}\)
3. \(15~\text{J}\)
4. \(9~\text{J}\)

Subtopic:  Work done by constant force |
 81%
Level 1: 80%+
AIPMT - 2013
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An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass \(1\) kg moves with a speed of \(12\) ms–1 and the second part of mass \(2\) kg moves with \(8\) ms–1 speed. If the third part flies off with \(4\) ms–1 speed, then its mass is:
1. \(5\) kg 2. \(7\) kg
3. \(17\) kg 4. \(3\) kg
Subtopic:  Collisions |
 71%
Level 2: 60%+
AIPMT - 2013
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The potential energy of a particle in a force field is \(U=\dfrac{A}{r^2}-\dfrac{B}{r}\) where \(A\) and \(B\) are positive constants and \(r\) is the distance of the particle from the centre of the field. For stable equilibrium, the distance of the particle is:
1. \(\dfrac{B}{A}\) 2. \(\dfrac{B}{2A}\)
3. \(\dfrac{2A}{B}\) 4. \(\dfrac{A}{B}\)
Subtopic:  Potential Energy: Relation with Force |
 79%
Level 2: 60%+
AIPMT - 2012
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Two spheres \(A\) and \(B\) of masses \(m_1\) and \(m_2,\) respectively, collide. \(A\) is at rest initially and \(B\) is moving with velocity \(v\) along the \(x\text-\)axis. After the collision, \(B\) has a velocity \(\frac{v}{2}\) in a direction perpendicular to the original direction. The mass \(A\) moves after collision in the direction:
1. same as that of \(B.\)
2. opposite to that of \(B.\)
3. \(\theta = \text{tan}^{-1}\left(\frac{1}{2} \right)\) to the positive \(x\)-axis.
4. \(\theta = \text{tan}^{-1}\left(\frac{-1}{2} \right )\) to the positive \(x\)-axis.
Subtopic:  Collisions |
Level 3: 35%-60%
AIPMT - 2012
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