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A : When a ring moves in pure rolling co...

A : When a ring moves in pure rolling condition on ground it has 50% translational and 50% rotational energy.
R : `(KE_("trans"))/(KE_("rot"))=((1)/(2)MV^(2))/((1)/(2)l omega^(2))=((1)/(2)MV^(2))/((1)/(2)(MR^(2))(V^(2))/(R^(2)))=1:1`

A

If both Assertion & Reason are true and the reason is the correct explanation of the assertion,

B

If both Assertion & Reason are true but the reason is not the correct explanation of the assertion,

C

If Assertion is true statement but Reason is false,

D

If both Assertion and Reason are false statements,

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the kinetic energy of a ring that is rolling without slipping. We will derive the translational and rotational kinetic energies and show that they are equal in a pure rolling condition. ### Step-by-Step Solution: 1. **Identify the Kinetic Energies**: - The translational kinetic energy (KE_trans) of the ring is given by: \[ KE_{\text{trans}} = \frac{1}{2} m v^2 \] - The rotational kinetic energy (KE_rot) of the ring is given by: \[ KE_{\text{rot}} = \frac{1}{2} I \omega^2 \] - For a ring, the moment of inertia \( I \) about its center is: \[ I = m R^2 \] 2. **Relate Angular Velocity and Linear Velocity**: - In pure rolling motion, the relationship between linear velocity \( v \) and angular velocity \( \omega \) is: \[ v = R \omega \] - Rearranging gives: \[ \omega = \frac{v}{R} \] 3. **Substitute \( \omega \) in the Rotational Kinetic Energy**: - Substitute \( \omega \) into the expression for \( KE_{\text{rot}} \): \[ KE_{\text{rot}} = \frac{1}{2} I \omega^2 = \frac{1}{2} (m R^2) \left(\frac{v}{R}\right)^2 \] - Simplifying this gives: \[ KE_{\text{rot}} = \frac{1}{2} m R^2 \cdot \frac{v^2}{R^2} = \frac{1}{2} m v^2 \] 4. **Compare the Kinetic Energies**: - Now we have: \[ KE_{\text{trans}} = \frac{1}{2} m v^2 \] \[ KE_{\text{rot}} = \frac{1}{2} m v^2 \] - Therefore, we can see that: \[ KE_{\text{trans}} = KE_{\text{rot}} \] 5. **Calculate the Total Kinetic Energy**: - The total kinetic energy (KE_total) is: \[ KE_{\text{total}} = KE_{\text{trans}} + KE_{\text{rot}} = \frac{1}{2} m v^2 + \frac{1}{2} m v^2 = m v^2 \] 6. **Find the Ratios**: - The ratio of translational kinetic energy to rotational kinetic energy is: \[ \frac{KE_{\text{trans}}}{KE_{\text{rot}}} = \frac{\frac{1}{2} m v^2}{\frac{1}{2} m v^2} = 1 \] ### Conclusion: - Since both the translational and rotational kinetic energies are equal, we conclude that in pure rolling conditions, a ring has 50% of its kinetic energy as translational and 50% as rotational. Thus, both statements A and R are correct.
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