Question

A ball is thrown vertically upward attains a maximum height of 45m. The time after which velocity of the ball become equal to half the velocity of projection?(use g=10m/s2).

Answer 1

Given :
Maximum Height =h=45m
acceleration due to gravity=-g= -10m/s²
Let u be the velocity of projection.
Time=t?
Velocity at maximum height, V=0 m/s
From second equation of motion:
v²-u²=2gh
0²-u²=-2gh
u²=2gh
u=√2gh
=√2x10x45
u=30m/s

Velocity of ball becomes half of projection velocity= V=15m/s
Time :
From first equation of motion :
v=U-gt
15=30(-10)xt
-30+15=-10t
-15=-10 t
t=15/10
 =1/5 sec

∴The time after which velocity of the ball become equal to half the velocity of projection is 1.5sec

Answer 2

Heya mate ,

Answer:

1.5 secs

THE EXPLANATION IS IN THE ATTACHMENT.......

Hope it helps u dear friend