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A stationary body explodes in to four id...

A stationary body explodes in to four identical fragments such that three of them fly mutually perpendicular to each other, each with same `KE(E_(0))`. The energy of explosion will be

A

`6E_(0)`

B

`3E_(0)`

C

`4E_(0)`

D

`2E_(0)`

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the explosion of a stationary body into four identical fragments, three of which move mutually perpendicular to each other, each with the same kinetic energy \(E_0\). We will find the total energy of the explosion. ### Step-by-Step Solution: 1. **Understanding the Initial Conditions:** - The body is stationary before the explosion, which means its initial momentum is zero. - After the explosion, it breaks into four identical fragments. 2. **Momentum Conservation:** - Since the initial momentum is zero, the total momentum after the explosion must also be zero. - Let the momentum of the three fragments moving along the x, y, and z axes be represented as \( \vec{p_1}, \vec{p_2}, \) and \( \vec{p_3} \). - The fourth fragment's momentum, \( \vec{p_4} \), can be expressed as: \[ \vec{p_4} = -(\vec{p_1} + \vec{p_2} + \vec{p_3}) \] 3. **Kinetic Energy of the Fragments:** - Each of the three fragments has a kinetic energy \(E_0\). The relationship between kinetic energy and momentum is given by: \[ E = \frac{p^2}{2m} \] - Therefore, for each of the three fragments: \[ E_0 = \frac{p_1^2}{2m} = \frac{p_2^2}{2m} = \frac{p_3^2}{2m} \] - This implies that the magnitudes of their momenta are equal: \[ p_1 = p_2 = p_3 = p_0 \] 4. **Calculating the Fourth Fragment's Momentum:** - The total momentum of the three fragments can be calculated as: \[ \vec{p_1} + \vec{p_2} + \vec{p_3} = p_0 \hat{i} + p_0 \hat{j} + p_0 \hat{k} \] - The magnitude of this total momentum is: \[ |\vec{p_1} + \vec{p_2} + \vec{p_3}| = \sqrt{p_0^2 + p_0^2 + p_0^2} = \sqrt{3}p_0 \] - Therefore, the momentum of the fourth fragment is: \[ p_4 = \sqrt{3}p_0 \] 5. **Kinetic Energy of the Fourth Fragment:** - The kinetic energy of the fourth fragment can be calculated as: \[ E_4 = \frac{p_4^2}{2m} = \frac{(\sqrt{3}p_0)^2}{2m} = \frac{3p_0^2}{2m} \] - Since \(E_0 = \frac{p_0^2}{2m}\), we can express \(E_4\) in terms of \(E_0\): \[ E_4 = 3E_0 \] 6. **Total Energy of the Explosion:** - The total energy of the explosion is the sum of the kinetic energies of all four fragments: \[ E_{\text{total}} = E_0 + E_0 + E_0 + E_4 = 3E_0 + 3E_0 = 6E_0 \] ### Final Answer: The energy of the explosion will be \(6E_0\).

To solve the problem, we need to analyze the explosion of a stationary body into four identical fragments, three of which move mutually perpendicular to each other, each with the same kinetic energy \(E_0\). We will find the total energy of the explosion. ### Step-by-Step Solution: 1. **Understanding the Initial Conditions:** - The body is stationary before the explosion, which means its initial momentum is zero. - After the explosion, it breaks into four identical fragments. ...
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Knowledge Check

  • 1 kg body explodes into three fragements. The ratio of their masses is 1 : 1: 3 . The fragments of same mass move perpendicular to each other with speed 30 m/s. The speed of heavier part is

    A
    `(10)/(sqrt(2))` m/s
    B
    `10sqrt(2)` m/s
    C
    `20sqrt(2)` m/s
    D
    `30sqrt(2)` m/s
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