Question

A stone is thrown vertically upward with speed v from point P. It passes through point Q, 30 m higher than P, with speed . If T is the time taken by the particle to return to point P, then value of T is (g = 10 m/s2)

Answer 1

Answer:

this answer............. ..................

Answer 2

Answer: 4.90 seconds

Step-by-step explanation:

• Case 1:-During upward motion

       Initial velocity u=v and final velocity v=0,S=30m

          $v^{2}-u^{2}=2gS$

     ⇒ $-v^{2}=2*10*30$

     ⇒$v^{2}=-\sqrt{600}$

     ∴ v= -24.5 m/s  

       We know,v=u+gt

                    ⇒0=v+10t

                    ⇒t=$\frac{-v}{10} s$

                    ⇒t=$\frac{-(-24.5)}{10}$

                    ∴ t=2.45s

• Case 2:-During downward motion

        u=0, and S=30m

        $v^{2}-u^{2}=2gS$

     ⇒$v^{2} =2*10*30$

     ⇒$v=\sqrt{600}$

    ∴ v=24.5 m/s

    Now,v=u+gt

          ⇒24.5=10t

          ∴ t=2.45s

• Total time T=(2.45+2.45)s

                             =4.90s

• Hence,total time T is 4.90 seconds.

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