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Question

A metallic bob X of mass m is released from position A. It collides elastically with another identical bob Y placed at rest at position B on a horizontal frictionless table. The angle AOB is 30°.

How high does the bob X rise immediately after the

This question was previously asked in
NDA 2 2024 GAT Question Paper (01-Sep-2024)
The correct answer is To the same height as that of position A on the other side in the same trajectory

Given:

A metallic bob X of mass m is released from position A. It collides

elastically with another identical bob Y placed at rest at position B. The

angle AOB is 30°.

Concept Used:

In an elastic collision between two identical masses, the moving mass

comes to rest, and the mass at rest starts moving with the velocity of the

first mass.

Formula Used:

Conservation of energy and conservation of momentum principles are

used. The height reached by the bob after the initial potential energy can

determine the collision.

Calculation

⇒ Initial potential energy of bob X at A:

⇒ PEA = mgh

⇒ h = L(1 - cos(θ)),

Where L is the length of the pendulum and θ is the angle.

⇒ h = L(1 - cos(30°))

⇒ h = L(1 - √3/2)

Since the collision is elastic and bobs are identical, bob Y will rise to the

same height on the other side. Hence,

The height reached by bob Y (initially bob X) = h = L(1 - √3/2)

∴ Bob X rises immediately after the collision to the same height as that of position A on the other side in the same trajectory.

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Similar Questions

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  2. In a carrom game, a striker of mass 15 g hits a coin of mass 5 g head on and the coin moves with a speed of 0.36 m/s. If the time of contact between the striker and the coin is 3 milliseconds, then what is the average force applied by the striker on the coin?


Important Questions from Collisions

  1. Two bodies collide each other and the collision is perfectly elastic. The co-efficient of restitution of these two bodies is

  2. During inelastic collision between two bodies, which of the following quantities always remain conserved?

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