Q. A car starts from rest and accelerates at 5 $m/s^2$. 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 = 6s ?
A) 20 m/s, 0
B) $20\sqrt{2}$ m/s, 0
C) $20\sqrt{2}$ m/s, 10 $m/s^2$
D) 20 m/s, 5 $m/s^2$
Explanation
[Solution] At release the ball has horizontal speed 20 m/s; after 2 s of free fall its vertical speed is 20 m/s, so v = $20\sqrt{2}$ m/s and a = g = 10 $m/s^2$. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.