Question

A body of mass m is thrown at an angle θ to the horizontal with the initial velocity u. Find the instantaneous power of gravity as function of time.

• A. mg(gt - u cos)
• B. mg(gt - u cot)
• C. mg(gt - u sin)
• D. mg(gt - u tan)

Answer 1

The correct option is C

mg(gt - u sin)

Now we find the instantaneous power of gravity at a instant t=t when particles has

Velocity v shown in figure. Tis velocity is vectorically given as

v=(u cos$\theta$)i + (u sin$\theta$ - gt)j and force vector on it is F =-mgj

Instantaneous power can be given as P = F.v

or (-mg j).(u cos$\theta$ i + u sin$\theta$ j - gt) or mg(gt - u sin$\theta$)