Gravitation

JEE Main level, single correct, medium

189 of 223

Question 189 of 223

A body A of mass mm is moving in a circular orbit of radius RR about a planet. Another body B of mass m2\dfrac{m}{2} collides with A with a velocity which is half (v⃗2)\left(\dfrac{\vec{v}}{2}\right) the instantaneous velocity v⃗\vec{v} of A. The collision is completely inelastic. Then, the combined body:

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Answer: (D) starts moving in an elliptical orbit around the planet

Conserving momentum
m2v2+mv=(m+m2)vf\dfrac{m}{2}\dfrac{v}{2}+mv=\left(m+\dfrac{m}{2}\right){v}_{f}
vf=2mV4×3m2=5V6{v}_{f}=\dfrac{2mV}{4\times \dfrac{3m}{2}}=\dfrac{5V}{6}
vf<vorb(=v){v}_{f}\lt {v}_{orb}\left(=v\right) thus the combined mass will go on to an elliptical path

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