Three different objects of mass m1, m2 and m3 are allowed to fall from rest and from the same point ‘O’ along three different frictionless paths. The speeds of the three objects, on reaching the ground, will be in the ratio of:

1. m1:m2:m3 2. m1:2m2:3m3
3. 1 : 1 : 1 4. 1m1:1m2:1m3 

Subtopic:  Work Energy Theorem |
 81%
Level 1: 80%+
AIIMS - 2002
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A man pushes a wall and fails to displace it. He does:
1. negative work
2. positive but not maximum work
3. no work at all
4. maximum work

Subtopic:  Concept of Work |
 88%
Level 1: 80%+
PMT - 1992
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The minimum work done in pulling up a block of wood weighing \(2\) kN for a length of \(10\) m on a smooth plane inclined at an angle of \(15^\circ\) with the horizontal is (given: \(\mathrm{sin}15^\circ=0.2588)\):
1. \(4.36\) kJ
2. \(5.17\) kJ
3. \(8.91\) kJ
4. \(9.82\) kJ

Subtopic:  Work done by constant force |
 81%
Level 1: 80%+
PMT - 2003
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A spherical ball of mass \(20\) kg is stationary at the top of a hill of height\(100\) m. It slides down a smooth surface to the ground, then climbs up another hill of height \(30\) m and finally slides down to a horizontal base at a height of \(20\) m above the ground. The velocity attained by the ball is: 
1. \(10 \) m/s
2. \(10 \sqrt{30} \) m/s
3. \(40 \) m/s
4. \(20 \) m/s

Subtopic:  Conservation of Mechanical Energy |
 64%
Level 2: 60%+
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A quarter horse-power motor runs at a speed of \(600~\text{rpm}\)Assuming \(40\%\) efficiency, the work done by the motor in one rotation will be:
1. \(7.46~\text{J}\)
2. \(7400~\text{J}\)
3. \(7.46~\text{ergs}\)
4. \(74.6~\text{J}\)

Subtopic:  Power |
 55%
Level 3: 35%-60%
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Two equal masses, \(m_1\) and \(m_2,\) moving in the same straight line at velocities \(+3~\text{m/s}\) and \(-5~\text{m/s}\) respectively, collide elastically. Their velocities after the collision will be:
1. \(+4~\text{m/s for both}\)
2. \(-3~\text{m/s}~\text{and}+5~\text{m/s}\)
3. \(-4~\text{m/s}~\text{and}+4~\text{m/s}\)
4. \(-5~\text{m/s}~\text{and}+3~\text{m/s}\)
Subtopic:  Collisions |
 83%
Level 1: 80%+
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A uniform chain of length \(L\) and mass \(M\) is lying on a smooth table and one-third of its length is hanging vertically down over the edge of the table. If \(g\) is the acceleration due to gravity, the work required to pull the hanging part on the table is:
1. \(MgL\)

2. \(\dfrac{MgL}{3}\)

3. \(\dfrac{MgL}{9}\)

4. \(\dfrac{MgL}{18}\)

Subtopic:  Gravitational Potential Energy |
 75%
Level 2: 60%+
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A particle of mass 'm' is moving in a horizontal circle of radius 'r' under a centripetal force equal to –K/r2, where K is a constant. The total energy of the particle will be:

1. K2r

2. K2r

3. Kr

4. Kr

Subtopic:  Potential Energy: Relation with Force |
 58%
Level 3: 35%-60%
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A force \(F = -k(y\hat i +x\hat j)\) (where \(k\) is a positive constant) acts on a particle moving in the \(xy\text-\)plane. Starting from the origin, the particle is taken along the positive \(x\text-\)axis to the point \((a,0)\) and then parallel to the \(y\text-\)axis to the point \((a,a)\). The total work done by the force on the particle is:
1. \(-2ka^2\)
2. \(2ka^2\)
3. \(-ka^2\)
4. \(ka^2\)

Subtopic:  Work Done by Variable Force |
 58%
Level 3: 35%-60%
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A lorry and a car moving with the same K.E. are brought to rest by applying the same retarding force, then:

1. Lorry will come to rest in a shorter distance

2. Car will come to rest in a shorter distance

3. Both will come to rest in a same distance

4. None of the above

Subtopic:  Work Energy Theorem |
 67%
Level 2: 60%+
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