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

Q 1 :
The bob of a pendulum was released from a horizontal position. The length of the pendulum is 10 m. If it dissipates 10% of its initial energy against air resistance, the speed with which the bob arrives at the lowest point is ______.

[Use, g = 10 ${ms}^{- 2}$ ] [2024]

$6 \sqrt{5} {ms}^{- 1}$
$5 \sqrt{5} {ms}^{- 1}$
$2 \sqrt{5} {ms}^{- 1}$
$5 \sqrt{6} {ms}^{- 1}$

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(1)

$ℓ = 10 m,$

Initial energy $= m g ℓ$

So, $\frac{9}{10} m g ℓ = \frac{1}{2} m v^{2}$

$\Rightarrow \frac{9}{10} \times 10 \times 10 = \frac{1}{2} v^{2}$

$v^{2} = 180$

$v = \sqrt{180} = 6 \sqrt{5} m/s$

Q 2 :
A particle is placed at the point A of a frictionless track ABC as shown in the figure. It is gently pushed towards the right. The speed of the particle when it reaches the point B is (Take g = 10 $m / s^{2}$ ). [2024]

$\sqrt{20}$ m/s
$\sqrt{10}$ m/s
$2 \sqrt{10}$ m/s
10 m/s

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(2)

By energy conservation

$| Δ P E |$ $=$ $| Δ K E |$

$m g (h_{2} - h_{1}) = (\frac{1}{2} m v^{2} - 0)$

$m g [0.5] = \frac{1}{2} m v^{2}$

$v = \sqrt{10} m/s$

Q 3 :
A disc of radius R and mass M is rolling horizontally without slipping with speed n. It then moves up an inclined smooth surface as shown in the figure. The maximum height that the disc can go up the incline is ______ [2024]

$\frac{v^{2}}{g}$
$\frac{3}{4} \frac{v^{2}}{g}$
$\frac{1}{2} \frac{v^{2}}{g}$
$\frac{2}{3} \frac{v^{2}}{g}$

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(3)

Rolling $v_{0} = ω R$

Conservation of energy, $K_{i} + U_{i} = K_{f} + U_{f}$

$\frac{1}{2} m v_{0}^{2} + \frac{1}{2} [\frac{M R^{2}}{2}] {\cdot (\frac{v_{0}}{R})}^{2} + 0 = m g h + \frac{1}{2} [\frac{M R^{2}}{2}] \cdot (\frac{v_{0}^{2}}{R^{2}})$

$\frac{1}{2} m v_{0}^{2} = m g h_{\max} \Rightarrow h_{\max} = \frac{v_{0}^{2}}{2 g}$

Topic Question Set

Q 1 :
The bob of a pendulum was released from a horizontal position. The length of the pendulum is 10 m. If it dissipates 10% of its initial energy against air resistance, the speed with which the bob arrives at the lowest point is ______.

[Use, g = 10 ${ms}^{- 2}$ ] [2024]

Q 2 :
A particle is placed at the point A of a frictionless track ABC as shown in the figure. It is gently pushed towards the right. The speed of the particle when it reaches the point B is (Take g = 10 $m / s^{2}$ ). [2024]

Q 3 :
A disc of radius R and mass M is rolling horizontally without slipping with speed n. It then moves up an inclined smooth surface as shown in the figure. The maximum height that the disc can go up the incline is ______ [2024]

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Topic Question Set

Q 1 : The bob of a pendulum was released from a horizontal position. The length of the pendulum is 10 m. If it dissipates 10% of its initial energy against air resistance, the speed with which the bob arrives at the lowest point is ______. [Use, g = 10 ms-2] [2024]

Q 2 : A particle is placed at the point A of a frictionless track ABC as shown in the figure. It is gently pushed towards the right. The speed of the particle when it reaches the point B is (Take g = 10 m/s2). [2024]

Q 3 : A disc of radius R and mass M is rolling horizontally without slipping with speed n. It then moves up an inclined smooth surface as shown in the figure. The maximum height that the disc can go up the incline is ______ [2024]

Want Us to Email you About Special Offers & Updates?

Q 1 :
The bob of a pendulum was released from a horizontal position. The length of the pendulum is 10 m. If it dissipates 10% of its initial energy against air resistance, the speed with which the bob arrives at the lowest point is ______.

[Use, g = 10 ${ms}^{- 2}$ ] [2024]

Q 2 :
A particle is placed at the point A of a frictionless track ABC as shown in the figure. It is gently pushed towards the right. The speed of the particle when it reaches the point B is (Take g = 10 $m / s^{2}$ ). [2024]

Q 3 :
A disc of radius R and mass M is rolling horizontally without slipping with speed n. It then moves up an inclined smooth surface as shown in the figure. The maximum height that the disc can go up the incline is ______ [2024]