Question

17. A body projected vertically upwards attains a maximum height of 450 m. Calculate the velocity of
projection
(1 Point)​

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moitsingar

16.12.2016

Physics

Secondary School

answered • expert verified

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).

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prmkulk1978

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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