A ball is projected vertically up from ground. Boy ' A ' standing at the window of first floor of a nearby building observes that the time interval between the ball crossing him while going up and the ball crossing him while going down is 2 s . Another boy B standing on the second floor notices the time interval between the ball passing him twice, during up and down motion is 1 s . Calculate the difference between the vertical positions of boy B and boy A . (Assume g = 10 m s - 2 )

Question

A ball is projected vertically up from ground. Boy ' A ' standing at the window of first floor of a nearby building observes that the time interval between the ball crossing him while going up and the ball crossing him while going down is 2 s . Another boy B standing on the second floor notices the time interval between the ball passing him twice, during up and down motion is 1 s . Calculate the difference between the vertical positions of boy B and boy A . (Assume g = 10 m s - 2 ), 8 . 45 m, 3 . 75 m, 4 . 25, 2 . 50 m

MARKS App · Accepted Answer

Let's assume v 1 and v 2 are the speeds of the ball while crossing the Boy A and B respectively during its motion. Applying the equation of motion, S = u t + 1 2 a t 2 for the motion of ball while passing the Boy A is ⇒ 0 = v 1 2 - 1 2 10 2 2 ⇒ v 1 = 10 m s - 1 . while passing the Boy B is ⇒ 0 = v 2 1 - 1 2 10 1 2 ⇒ v 1 = 5 m s - 1 . The difference between the vertical positions of the boys A and B is v 2 2 = v 1 2 - 2 g h ⇒ 5 2 = 10 2 - 2 10 h ⇒ h = 100 - 25 20 = 3 . 75 m .

Search any question & find its solution

Looking for more such questions to practice?