Question

Two balls of equal mass are projected from a tower simultaneously with equal speeds. One at angle $\theta$ above the horizontal and the other at the same angle $\theta$ below the horizontal. The path of the centre of mass of the two balls is

• A. a vertical straight line
• B. a horizontal straight line
• C. a straight line at angle $\alpha (<\theta )$ with horizontal
• D. a parabola

Answer 1

The correct option is D a parabola

As we can see that both have same $horizontal$ velocity as $vcos\theta$

and their vertical velocities will be equal but opposite so the $vertical$ velocity of center of mass will be $zero$ and the

horizontal one will be $\frac{mvcos\theta +mvcos\theta }{m+m}=vcos\theta$

so this will be look like $a$ mass having mass $2m$ has been thrown $horizontally$ under $gravity$ so the path will be $parabolic.$