Question

Two particles of mass $M$ and $2M$ are at a distance $D$ apart. Under their mutual force they start moving towards each other. The acceleration of their centre of mass when they are $\frac{D}{2}$ apart is:

• A. $\frac{2GM}{D^2}$
• B. $\frac{4GM}{D^2}$
• C. $\frac{8GM}{D^2}$
• D. Zero

Answer 1

The correct option is D Zero

Since, initially the accelerations of both the particles are zero, so acceleration of centre of mass is also zero initially. Now the two particles are moving towards each other under mutual attraction, so net force acting on the system is zero. Thus the acceleration of centre of mass is still zero at every instant.