Question

22. A ball is projected from a point O as shown in figure.
It will strike the ground after (g = 10 m/s2)
10 m/s
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Answer 1

Explanation:

Time period of projectile motion:

T= 2usinθ/g

=10×2×sin30 /10

=2/2

1

=1s

Then for vertically downward motion:

initial velocity (u y)=10sin30

=5 m/s

a=g and h=60m

So applying equation h=ut+ 1/2at 2

⇒60=5t+ 1/2(10)t ^2

⇒60=5t+5t ^2

or t ^2+t−12=0

(t−3)(t+4)=0

⇒t=3s (t=−4s is not possible)

Therefore total time of flight =T+t=4s.