Work Energy and Power | Physics JEE previous year questions with Solutions

Q 1 :
A bullet of mass 50g is fired with a speed 100 m/s on a plywood and emerges with 40 m/s. The percentage loss of kinetic energy is [2024]

44%
32%
84%
16%

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(C) $K_{i} = \frac{1}{2} m {(100)}^{2}$ and $K_{f} = \frac{1}{2} m {(40)}^{2}$

$% l o s s = \frac{| K_{f} - K_{i} |}{K_{i}} \times 100 = \frac{| \frac{1}{2} m {(40)}^{2} - \frac{1}{2} m {(100)}^{2} |}{\frac{1}{2} m {(100)}^{2}} \times 100$

$= \frac{| 1600 - 100 \times 100 |}{100} = 84 %$

Q 2 :
Four particles A, B, C, D of mass $\frac{m}{2}, m, 2 m, 4 m$ have same momentum, respectively. The particle with maximum kinetic energy is: [2024]

A
D
B
C

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(A) Kinetic energy = $\frac{P^{2}}{2 m}$

$P \Rightarrow$ momentum (same for all)

$K E \propto \frac{1}{m a s s}$

Particle A is of least mass, has maximum kinetic energy

Q 3 :
When kinetic energy of a body becomes 36 times of its original value, the percentage increase in the momentum of the body will be [2024]

600%
500%
60%
6%

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(B) Kinetic energy $(K) = \frac{P^{2}}{2 m} \Rightarrow P = \sqrt{2 m K}$

If $K_{f} = 36$ $K_{i} .$ So $P_{f} = 6$ $P_{i}$

% increase in momentum

$= \frac{P_{f} - P_{i}}{P_{i}} \times 100 % = \frac{6 P_{i} - P_{i}}{P_{i}} \times 100 % = 500 % \Rightarrow ∆ P % = 500 %$

Q 4 :
Three bodies A, B and C have equal kinetic energies and their masses are 400 g, 1.2 kg and 1.6 kg respectively. The ratio of their linear momenta is [2024]

$1 : \sqrt{3} : 2$
$1 : \sqrt{3} : \sqrt{2}$
$\sqrt{3} : \sqrt{2} : 1$
$\sqrt{2} : \sqrt{3} : 1$

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(A) $K_{A} = K_{B} = K_{C}$

Momentum $P = \sqrt{2 m K}$

$P \propto \sqrt{m}$

$P_{A} : P_{B} : P_{C} = \sqrt{m_{A}} : \sqrt{m_{B}} : \sqrt{m_{C}}$

$= \sqrt{400} : \sqrt{1200} : \sqrt{1600}$

$= 20 : 20 \sqrt{3} : 40$

$= 1 : \sqrt{3} : 2$

Q 5 :
A particle of mass m moves on a straight line with its velocity increasing with distance according to the equation $v = α \sqrt{x},$ where $α$ is a constant. The total work done by all the forces applied on the particle during its displacement from $x = 0$ to $x = d,$ will be [2024]

$\frac{m}{2 α^{2} d}$
$\frac{m d}{2 α^{2}}$
$\frac{m α^{2} d}{2}$
$2 m α^{2} d$

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(C) $v = α \sqrt{x}$

at $x = 0 : v = 0$ and at $x = d; v = α \sqrt{d}$

W.D. $= K_{f} - K_{i}$

W.D. $= \frac{1}{2} m {(α \sqrt{d})}^{2} - \frac{1}{2} m {(0)}^{2}$

$\Rightarrow$ W.D $= \frac{m α^{2} d}{2}$

Q 6 :
Two bodies of mass 4g and 25g are moving with equal kinetic energies. The ratio of magnitude of their linear momentum is [2024]

3 : 5
5 : 4
2 : 5
4 : 5

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(C) $\frac{P_{1}^{2}}{2 m_{1}} = \frac{P_{2}^{2}}{2 m_{2}}$

$\frac{P_{1}}{P_{2}} = \sqrt{\frac{m_{1}}{m_{2}}} = \frac{2}{5}$

Q 7 :
An artillery piece of mass $M_{1}$ fires a shell of mass $M_{2}$ horizontally. Instantaneously after the firing, the ratio of kinetic energy of the artillery and that of the shell is [2024]

$\frac{M_{1}}{M_{1} + M_{2}}$
$\frac{M_{2}}{M_{1} + M_{2}}$
$\frac{M_{1}}{M_{2}}$
$\frac{M_{2}}{M_{1}}$

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(D) $| \vec{p_{1}} | = | \vec{p_{2}} |$

$K E = \frac{p^{2}}{2 M} \Rightarrow$ $K E \propto \frac{1}{m}$

$\frac{K E_{1}}{K E_{2}} = \frac{p^{2} / 2 M_{1}}{p^{2} / 2 M_{2}} = \frac{M_{2}}{M_{1}}$

Topic Question Set

Q 1 :
A bullet of mass 50g is fired with a speed 100 m/s on a plywood and emerges with 40 m/s. The percentage loss of kinetic energy is [2024]

Q 2 :
Four particles A, B, C, D of mass $\frac{m}{2}, m, 2 m, 4 m$ have same momentum, respectively. The particle with maximum kinetic energy is: [2024]

Q 3 :
When kinetic energy of a body becomes 36 times of its original value, the percentage increase in the momentum of the body will be [2024]

Q 4 :
Three bodies A, B and C have equal kinetic energies and their masses are 400 g, 1.2 kg and 1.6 kg respectively. The ratio of their linear momenta is [2024]

Q 5 :
A particle of mass m moves on a straight line with its velocity increasing with distance according to the equation $v = α \sqrt{x},$ where $α$ is a constant. The total work done by all the forces applied on the particle during its displacement from $x = 0$ to $x = d,$ will be [2024]

Q 6 :
Two bodies of mass 4g and 25g are moving with equal kinetic energies. The ratio of magnitude of their linear momentum is [2024]

Q 7 :
An artillery piece of mass $M_{1}$ fires a shell of mass $M_{2}$ horizontally. Instantaneously after the firing, the ratio of kinetic energy of the artillery and that of the shell is [2024]

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Topic Question Set

Q 1 : A bullet of mass 50g is fired with a speed 100 m/s on a plywood and emerges with 40 m/s. The percentage loss of kinetic energy is [2024]

Q 2 : Four particles A, B, C, D of mass m2,m,2m,4m have same momentum, respectively. The particle with maximum kinetic energy is: [2024]

Q 3 : When kinetic energy of a body becomes 36 times of its original value, the percentage increase in the momentum of the body will be [2024]

Q 4 : Three bodies A, B and C have equal kinetic energies and their masses are 400 g, 1.2 kg and 1.6 kg respectively. The ratio of their linear momenta is [2024]

Q 5 : A particle of mass m moves on a straight line with its velocity increasing with distance according to the equation v=αx, where α is a constant. The total work done by all the forces applied on the particle during its displacement from x=0 to x=d, will be [2024]

Q 6 : Two bodies of mass 4g and 25g are moving with equal kinetic energies. The ratio of magnitude of their linear momentum is [2024]

Q 7 : An artillery piece of mass M1 fires a shell of mass M2 horizontally. Instantaneously after the firing, the ratio of kinetic energy of the artillery and that of the shell is [2024]

Want Us to Email you About Special Offers & Updates?

Q 1 :
A bullet of mass 50g is fired with a speed 100 m/s on a plywood and emerges with 40 m/s. The percentage loss of kinetic energy is [2024]

Q 2 :
Four particles A, B, C, D of mass $\frac{m}{2}, m, 2 m, 4 m$ have same momentum, respectively. The particle with maximum kinetic energy is: [2024]

Q 3 :
When kinetic energy of a body becomes 36 times of its original value, the percentage increase in the momentum of the body will be [2024]

Q 4 :
Three bodies A, B and C have equal kinetic energies and their masses are 400 g, 1.2 kg and 1.6 kg respectively. The ratio of their linear momenta is [2024]

Q 5 :
A particle of mass m moves on a straight line with its velocity increasing with distance according to the equation $v = α \sqrt{x},$ where $α$ is a constant. The total work done by all the forces applied on the particle during its displacement from $x = 0$ to $x = d,$ will be [2024]

Q 6 :
Two bodies of mass 4g and 25g are moving with equal kinetic energies. The ratio of magnitude of their linear momentum is [2024]

Q 7 :
An artillery piece of mass $M_{1}$ fires a shell of mass $M_{2}$ horizontally. Instantaneously after the firing, the ratio of kinetic energy of the artillery and that of the shell is [2024]