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A ball of mass 1kg is dropped from a hei...

A ball of mass 1kg is dropped from a height of h = 5m. It rebounds losing 50% of its total mechanical energy during collision. Then choose the correct statement(s) from the following .

A

After collision speed of ball is `5m//s`

B

After collision speed of ball is `5 sqrt(2) m//s`

C

The value of impulse is `( 10 - 5 sqrt( 2)) Ns`.

D

The value of impulse is `( 10 + 5 sqrt(2)) Ns`

Text Solution

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The correct Answer is:
To solve the problem step by step, we will analyze the motion of the ball, calculate its mechanical energy, and determine the impulse after the collision. ### Step 1: Calculate the initial potential energy (PE) of the ball The potential energy when the ball is at height \( h = 5 \, \text{m} \) is given by the formula: \[ PE = mgh \] Where: - \( m = 1 \, \text{kg} \) (mass of the ball) - \( g = 10 \, \text{m/s}^2 \) (acceleration due to gravity) - \( h = 5 \, \text{m} \) (height) Substituting the values: \[ PE = 1 \times 10 \times 5 = 50 \, \text{J} \] ### Step 2: Determine the kinetic energy (KE) just before the collision Just before the ball hits the ground, all its potential energy is converted into kinetic energy. Therefore: \[ KE = PE = 50 \, \text{J} \] ### Step 3: Calculate the velocity of the ball just before the collision Using the kinetic energy formula: \[ KE = \frac{1}{2} mv^2 \] Setting \( KE = 50 \, \text{J} \): \[ 50 = \frac{1}{2} \times 1 \times v^2 \] Solving for \( v^2 \): \[ v^2 = 100 \implies v = 10 \, \text{m/s} \] ### Step 4: Calculate the mechanical energy after the collision The problem states that the ball loses 50% of its total mechanical energy during the collision. Therefore, the mechanical energy after the collision is: \[ \text{Mechanical Energy after collision} = 50 \, \text{J} \times 0.5 = 25 \, \text{J} \] ### Step 5: Determine the velocity after the collision After the collision, the potential energy is again zero (as it is at ground level), so the kinetic energy after the collision is: \[ KE' = 25 \, \text{J} \] Using the kinetic energy formula: \[ KE' = \frac{1}{2} mu'^2 \] Setting \( KE' = 25 \, \text{J} \): \[ 25 = \frac{1}{2} \times 1 \times u'^2 \] Solving for \( u'^2 \): \[ u'^2 = 50 \implies u' = 5\sqrt{2} \, \text{m/s} \] ### Step 6: Calculate the impulse Impulse is defined as the change in momentum. The initial momentum just before the collision is: \[ p_{\text{initial}} = mv = 1 \times 10 = 10 \, \text{kg m/s} \] The final momentum after the collision is: \[ p_{\text{final}} = mu' = 1 \times 5\sqrt{2} \, \text{kg m/s} \] Calculating the impulse: \[ \text{Impulse} = p_{\text{final}} - p_{\text{initial}} = (5\sqrt{2} - 10) \, \text{kg m/s} \] ### Conclusion The ball rebounds with a speed of \( 5\sqrt{2} \, \text{m/s} \) and the impulse experienced by the ball is \( 5\sqrt{2} - 10 \, \text{kg m/s} \).
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