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Two balls of same mass are dropped from ...

Two balls of same mass are dropped from the same height h, on to the floor. The first ball bounces to a height `h//4`, after the collision & the second ball to a height `h//16`. The impulse applied by the first & second ball on the floor are `I_(1)` and `I_(2)` respectively. Then :-

A

`5I_(1) = 6I_(2)`

B

`6I_(1) = 5I_(1)`

C

`I_(1) = 2I_(2)`

D

`2I_(1) = I_(2)`

Text Solution

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The correct Answer is:
To solve the problem, we need to calculate the impulse applied by each ball on the floor and then find the ratio of these impulses. ### Step-by-Step Solution: 1. **Determine the initial velocity before impact for both balls:** The initial velocity \( V_i \) just before hitting the ground can be calculated using the formula: \[ V_i = \sqrt{2gh} \] 2. **Calculate the final velocity after bouncing for the first ball:** The first ball bounces to a height of \( \frac{h}{4} \). The final velocity \( V_{f1} \) after bouncing can be calculated using: \[ V_{f1} = \sqrt{2g \left(\frac{h}{4}\right)} = \sqrt{\frac{2gh}{4}} = \frac{1}{2} \sqrt{2gh} = \frac{1}{2} V_i \] 3. **Calculate the impulse \( I_1 \) for the first ball:** Impulse is defined as the change in momentum. The initial momentum \( P_i \) and final momentum \( P_f \) for the first ball are: \[ P_i = M V_i \quad \text{(downward)} \] \[ P_f = -M V_{f1} \quad \text{(upward)} \] Therefore, the impulse \( I_1 \) is: \[ I_1 = P_f - P_i = -M V_{f1} - M V_i = -M \left(\frac{1}{2} V_i\right) - M V_i = -\frac{3}{2} M V_i \] 4. **Calculate the final velocity after bouncing for the second ball:** The second ball bounces to a height of \( \frac{h}{16} \). The final velocity \( V_{f2} \) after bouncing can be calculated using: \[ V_{f2} = \sqrt{2g \left(\frac{h}{16}\right)} = \sqrt{\frac{2gh}{16}} = \frac{1}{4} \sqrt{2gh} = \frac{1}{4} V_i \] 5. **Calculate the impulse \( I_2 \) for the second ball:** Similarly, the initial and final momentum for the second ball are: \[ P_i = M V_i \quad \text{(downward)} \] \[ P_f = -M V_{f2} \quad \text{(upward)} \] Therefore, the impulse \( I_2 \) is: \[ I_2 = P_f - P_i = -M V_{f2} - M V_i = -M \left(\frac{1}{4} V_i\right) - M V_i = -\frac{5}{4} M V_i \] 6. **Find the ratio of impulses \( \frac{I_1}{I_2} \):** Now we can find the ratio of the impulses: \[ \frac{I_1}{I_2} = \frac{-\frac{3}{2} M V_i}{-\frac{5}{4} M V_i} = \frac{\frac{3}{2}}{\frac{5}{4}} = \frac{3}{2} \cdot \frac{4}{5} = \frac{12}{10} = \frac{6}{5} \] ### Final Result: The ratio of the impulses is: \[ \frac{I_1}{I_2} = \frac{6}{5} \]

To solve the problem, we need to calculate the impulse applied by each ball on the floor and then find the ratio of these impulses. ### Step-by-Step Solution: 1. **Determine the initial velocity before impact for both balls:** The initial velocity \( V_i \) just before hitting the ground can be calculated using the formula: \[ V_i = \sqrt{2gh} ...
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ALLEN-CENTRE OF MASS-EXERCISE-I
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