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A sphere is moving on a smooth surface w...

A sphere is moving on a smooth surface with angular velocity `omega` and linear velocity v. If collides elastically with another identical sphere B kept at rest. Neglecting friction everywhere, let `V_(A)` and `omega_(A)` be linear and angular velocities of sphere A after the impact and let `V_(B)` and `omega_(B)` be the corresponding parameters for spehre B. Then

A

`V_(A) =0, omega_(A) = 0`

B

`V_(B) = v, omega_(B) = 0`

C

`V_(B) =0, omega_(B) = omega`

D

`omega_(A) = 0 , omega_(B) = omega`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem of two identical spheres colliding elastically, we can break it down into a few steps. ### Step-by-Step Solution: 1. **Understanding the Situation**: - Sphere A is moving with a linear velocity \( v \) and an angular velocity \( \omega \). - Sphere B is at rest. - The collision is elastic, meaning both momentum and kinetic energy are conserved. 2. **Conservation of Linear Momentum**: - Before the collision, the total linear momentum is given by: \[ P_{\text{initial}} = m \cdot v + 0 = mv \] - After the collision, let \( V_A \) and \( V_B \) be the linear velocities of spheres A and B respectively. The total linear momentum after the collision is: \[ P_{\text{final}} = m \cdot V_A + m \cdot V_B \] - Setting the initial and final momenta equal gives: \[ mv = mV_A + mV_B \] - Dividing through by \( m \) (assuming \( m \neq 0 \)): \[ v = V_A + V_B \] 3. **Conservation of Kinetic Energy**: - The initial kinetic energy is: \[ KE_{\text{initial}} = \frac{1}{2} mv^2 + 0 = \frac{1}{2} mv^2 \] - The final kinetic energy is: \[ KE_{\text{final}} = \frac{1}{2} m V_A^2 + \frac{1}{2} m V_B^2 \] - Setting the initial and final kinetic energies equal gives: \[ \frac{1}{2} mv^2 = \frac{1}{2} m V_A^2 + \frac{1}{2} m V_B^2 \] - Dividing through by \( \frac{1}{2} m \) (again assuming \( m \neq 0 \)): \[ v^2 = V_A^2 + V_B^2 \] 4. **Analyzing the Collision**: - Since the collision is elastic and the spheres are identical, we can conclude that the velocities are exchanged. - Thus, after the collision: \[ V_A = 0 \quad \text{(Sphere A comes to rest)} \] \[ V_B = v \quad \text{(Sphere B moves with the initial velocity of A)} \] 5. **Angular Velocity**: - The angular velocity of sphere A after the collision remains unchanged because the collision does not affect the angular motion. Therefore: \[ \omega_A = \omega \quad \text{(remains the same)} \] - Sphere B, being at rest initially and not spinning, will have: \[ \omega_B = 0 \] ### Conclusion: - After the collision: - \( V_A = 0 \) - \( \omega_A = \omega \) - \( V_B = v \) - \( \omega_B = 0 \) ### Final Answer: The correct option is: - \( V_A = 0 \), \( \omega_A = \omega \), \( V_B = v \), \( \omega_B = 0 \)
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