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A body A is thrown up vertically from th...

A body A is thrown up vertically from the ground with velocity `V_(0)` and another body B is simultaneously dropped from a height H. They meet at a height `(H)/(2)` if `V_(0)` is equal to

A

`sqrt(150), 12`

B

`sqrt(160), 20`

C

`sqrt(200), 30`

D

`sqrt(150), 20`

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the motion of both bodies A and B and use the equations of motion to find the initial velocity \( V_0 \) of body A when they meet at a height \( \frac{H}{2} \). ### Step-by-Step Solution 1. **Identify the motion of body B**: Body B is dropped from a height \( H \) with an initial velocity of \( 0 \). The distance it travels when they meet at height \( \frac{H}{2} \) is: \[ s_B = H - \frac{H}{2} = \frac{H}{2} \] 2. **Use the second equation of motion for body B**: The second equation of motion states: \[ s = ut + \frac{1}{2} a t^2 \] For body B: - Initial velocity \( u = 0 \) - Acceleration \( a = g \) (downward) - Distance \( s = -\frac{H}{2} \) (since we take downward as negative) Plugging in the values: \[ -\frac{H}{2} = 0 \cdot t_B + \frac{1}{2} (-g) t_B^2 \] Simplifying this gives: \[ -\frac{H}{2} = -\frac{1}{2} g t_B^2 \] Rearranging, we find: \[ g t_B^2 = H \quad \Rightarrow \quad t_B^2 = \frac{H}{g} \] Therefore: \[ t_B = \sqrt{\frac{H}{g}} \] 3. **Identify the motion of body A**: Body A is thrown upward with an initial velocity \( V_0 \). The distance it travels when they meet at height \( \frac{H}{2} \) is: \[ s_A = \frac{H}{2} \] 4. **Use the second equation of motion for body A**: For body A: - Initial velocity \( u = V_0 \) - Acceleration \( a = -g \) (upward motion against gravity) - Distance \( s = \frac{H}{2} \) Plugging in the values: \[ \frac{H}{2} = V_0 t_A - \frac{1}{2} g t_A^2 \] 5. **Equate the time of both bodies**: Since both bodies meet at the same time, we have \( t_A = t_B \): \[ t_A = \sqrt{\frac{H}{g}} \] 6. **Substituting \( t_A \) into the equation for body A**: Substitute \( t_A \) into the equation for body A: \[ \frac{H}{2} = V_0 \left(\sqrt{\frac{H}{g}}\right) - \frac{1}{2} g \left(\sqrt{\frac{H}{g}}\right)^2 \] Simplifying the second term: \[ \frac{H}{2} = V_0 \sqrt{\frac{H}{g}} - \frac{1}{2} g \cdot \frac{H}{g} \] \[ \frac{H}{2} = V_0 \sqrt{\frac{H}{g}} - \frac{H}{2} \] 7. **Rearranging to solve for \( V_0 \)**: Adding \( \frac{H}{2} \) to both sides: \[ H = V_0 \sqrt{\frac{H}{g}} \] Now, solving for \( V_0 \): \[ V_0 = \frac{H}{\sqrt{\frac{H}{g}}} \] \[ V_0 = \sqrt{gH} \] ### Final Answer: \[ V_0 = \sqrt{gH} \]

To solve the problem, we need to analyze the motion of both bodies A and B and use the equations of motion to find the initial velocity \( V_0 \) of body A when they meet at a height \( \frac{H}{2} \). ### Step-by-Step Solution 1. **Identify the motion of body B**: Body B is dropped from a height \( H \) with an initial velocity of \( 0 \). The distance it travels when they meet at height \( \frac{H}{2} \) is: \[ s_B = H - \frac{H}{2} = \frac{H}{2} ...
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