Question

Question 4 (1d motion, constant a) You toss a set of keys straight up to a window that is 5 meters above you. The best way for the keys to be caught is for the keys to stop right in front of the window so you do that. Assume gravity produces an acceleration of 10 m/s/s downward. a. How fast should the keys leave your hand? b. How much time does it take the keys to reach the window?

Answer 1

Given: - i) Height of window from hand, S = 5 m/s ii) Acceleration due to gravity, g = 10 m/s^2 i) On reaching a height of 5 m, final velocity of keys will becomes zero Hence, v^2 = U^2 + 2as implies 0^2 = U^2 + 2 times (-10) times 5 implies U^2 = 100 implies U = 10 m/s ii) we know, v = U + at implies 0 = 10 + (-10) t implies 10 t = 10 implies t = 1 sec