Question

a ball thrown vertically upward returns to trower after 6 s​

Answer 1

Answer:

Explanation:

Total time of flight(t)=6s

So time to reach the maximum height =3s

if u= projected velocity then: 0=u−gt/2

⇒u=  1/2 gt

=  60 /2

​=30 m/s

Applying equation v ²=u²-2gh

0=900−20h

⇒h=45m

When the ball is at height 5m from highest point, it's height from ground =45−5=40m

Applying equation: s=ut+  1/2at²

(at h=40m)

⇒40=30t−  5t²

⇒t²-6t+8=0

As one root of the equation is given as: t 1=2s

By product of roots t  1  t  2 =8

⇒t 2  =4s. (when the ball reaches the same height again)

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