Discussion Forum

1)

A rocket is moving in a gravity-free space with a constant acceleration of 2 ms^-2 along +x direction (see figure). The length of a chamber inside the rocket is 4m. A  ball is thrown from the left and end of the chamber in+x direction with a speed of 0.3 ms^-1 relatives to the rocket. At the same time, another ball is thrown in  -x direction with a speed of 0.2 ms^-1 from its right and relative to the rocket. The time in seconds when the two balls hit each other is 

Answer:

Option B

Explanation:

Motion of ball A relative to rocket.

 Consider motion of two balls with respect to rocket.

 Maximum distance of ball A from left wall

    $\frac{u^{2}}{2a}=\frac{0.3\times0.3}{2\times2}$

  = $\frac{0.09}{4}=0.02m$      (as   $0=u^{2}-2as)$

 So, collision of two balls will take place very near to left wall

 Motion of ball B relative to  rocket

  For B      $S=ut+\frac{1}{2}at^{2}$

  $-4=-0.2t-(\frac{1}{2})2t^{2}$

   Solving this equation, we get,

  t= 1.9 s

Nearest integer =2s