Question

A boy standing on a long railroad car throws a ball straight upwards. The car is moving on the horizontal road with an acceleration of $1m/s^2$ and the projection speed in the vertical direction is $9.8m/s$. How far behind the boy will the ball fall on the car?

• A. $2m$
• B. $5m$
• C. $1m$
• D. $7m$

Answer 1

The correct option is A $2m$

Let the initial velocity of car be '$u$'. time of flight,
$t=\frac{2u_y}{g}=2$
Where, $u_y$ = component of velocity in vertical direction
Distance travelled by car
$x_c=u\times 2+\frac{1}{2}\times 1\times 2^2$
$=$$2u+2$
distance travelled by ball
$x_b=u\times 2$
$x_c-x_b=2u+2-2u$
$=$$2m$