Question

Astronauts Mr. X and Mr. Y float in gravity zero space with no relative velocity to one another. Mr. Y throws a mass of 5 kg towards X with speed 2 ms${}^{-1}$. If Mr. X catches it the changes in velocity of X and Y are :

• A. 0.21 ms${}^{-1}$, 0.80 ms${}^{-1}$
• B. 0.80 ms${}^{-1}$, 0.21 ms${}^{-1}$
• C. 0.12 ms${}^{-1}$, 0.08 ms${}^{-1}$
• D. 0.08 ms${}^{-1}$, 0.12 ms${}^{-1}$

Answer 1

The correct option is D 0.08 ms${}^{-1}$, 0.12 ms${}^{-1}$

Using conservation of momentum,
$(120+5)v_x=5\times 2$

or $v_x=\frac{10}{125}=0.08m{s}^{-1}$

Also $(90-5)v_y=5\times 2$

or $v_y=\frac{10}{85}=0.12m{s}^{-1}$