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NEET PHYSICSWORK, ENERGY AND POWERMedium

Question

Two spheres A and B of masses m1m_1 and m2m_2 respectively collide. A is at rest initially and B is moving with velocity vv along x-axis. After collision B has a velocity v2\frac{v}{2} in a direction perpendicular to the original direction. The mass A moves after collision in the direction:

A

same as that of B

B

opposite to that of B

C

θ=tan1(12)\theta = \tan^{-1}(\frac{1}{2}) to the x-axis

D

θ=tan1(12)\theta = \tan^{-1}(-\frac{1}{2}) to the x-axis

Step-by-Step Solution

  1. Identify the System: This is a two-dimensional collision problem. Sphere A (mass m1m_1) is initially stationary (uA=0u_A = 0). Sphere B (mass m2m_2) moves along the x-axis with velocity vv (uB=vi^u_B = v\hat{i}). After collision, B moves perpendicular to the original direction (along y-axis) with velocity v/2v/2 (vB=v2j^v_B = \frac{v}{2}\hat{j}).
  2. Apply Conservation of Linear Momentum: Total initial momentum equals total final momentum. Pinitial=m1uA+m2uB=0+m2vi^=m2vi^\vec{P}_{initial} = m_1 u_A + m_2 u_B = 0 + m_2 v \hat{i} = m_2 v \hat{i} Pfinal=m1vA+m2vB=m1vA+m2v2j^\vec{P}_{final} = m_1 \vec{v}_A + m_2 \vec{v}_B = m_1 \vec{v}_A + m_2 \frac{v}{2} \hat{j} Equating momenta: m2vi^=m1vA+m2v2j^m_2 v \hat{i} = m_1 \vec{v}_A + m_2 \frac{v}{2} \hat{j}.
  3. Solve for vA\vec{v}_A: m1vA=m2vi^m2v2j^m_1 \vec{v}_A = m_2 v \hat{i} - m_2 \frac{v}{2} \hat{j} vA=m2vm1i^m2v2m1j^\vec{v}_A = \frac{m_2 v}{m_1} \hat{i} - \frac{m_2 v}{2m_1} \hat{j}
  4. Determine Direction (θ\theta): The angle θ\theta with the x-axis is given by tanθ=vAyvAx\tan \theta = \frac{v_{Ay}}{v_{Ax}}. tanθ=m2v2m1m2vm1=12\tan \theta = \frac{- \frac{m_2 v}{2m_1}}{\frac{m_2 v}{m_1}} = -\frac{1}{2} θ=tan1(12)\theta = \tan^{-1}\left(-\frac{1}{2}\right) This indicates the direction is at an angle below the x-axis [Class 11 Physics, Ch 6, Sec 5.11.3].

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from WORK, ENERGY AND POWER. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSWORK, ENERGY AND POWERspheresmassesrespectivelycollideinitially

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