Question

An open lift is moving upwards with velocity $10m/s$. It has an upward acceleration of $2$ $m/s^2.$ A ball is projected upwards with velocity $20m/s$ relative to ground. Find displacement of lift and ball at that instant.

Answer 1

Distance covered by lift $=$ distance covered by ball

$10t+\frac{1}{2}\times 2t^2$$=20t-\frac{1}{2}\times 10t^2⟹10t-4t^2=0⟹t=\frac{5}{3}$

distance travelled$=10\times \left(5/3\right)+\frac{1}{2}\times 2\times (5/3{)}^2=19.44m$