A ball is projected with a velocity, $10{ \mathrm{m} \mathrm{s}}^{-1}$, at an angle of $60°$ with the vertical direction. Its speed at the highest point of its trajectory will be

A car starts from rest and accelerates at $5 \mathrm{m} {\mathrm{s}}^{-2}, \text{at} t=4 \mathrm{s}$, a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at $t=6 \mathrm{s}$ ? $(\left.g=10 \mathrm{m} {\mathrm{s}}^{-2}\right)$