A car starts from rest and accelerates at 5 m/s². At t = 4 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 s? (Take g = 10 m/s²)

Velocity of the car at t = 4 sec is
V_x = at = 4 × 5 = 20 m/s
So horizontal velocity = 20 m/s (remain constant)
Vertical velocity at t = 6 sec
i.e. after 2 sec of free fall
V_y = gt = 20 m/s
So net velocity $=\sqrt{{20}^2+{20}^2}=20\sqrt{2}\mathrm{m}/\mathrm{s}$
and once it starts falling acceleration is only ‘g’
i.e., 10 m/s²