-->

Motion In A Plane

Question
CBSEENPH11020861

A body is projected vertically upwards. The times corresponding to height h while ascending and while descending are t1 and t2, respectively.

  • gt1t22

  • g(t1 +t2)2

  • gt1t2

  • gt1t2(t1+t2)

Solution

B.

g(t1 +t2)2

Let v be the initial velocity of vertical projection and t be time taken by the body to reach a height h from the ground.

Here u = u,

a = -g,

s = h,

t = t

Using, 

ut + 12 (-g)t2 or gt2 - 2ut + 2h = 0 t = 2u± 4u2 - 4g x 2h2g = u± u2 -2ghgIt means t has two values, i.e.,t1 = u + u2 -2ghgt2 = u- u2-2ghgt1 +t2 = 2ug or u = g (t1 +t2)2