Question

A body of mass m is projected at an angle theta to the horizontal with an initial velocity u. The mean power of gravity over the whole time of journey is

Answer 1

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Answer 2

Answer:

Explanation:

Given,

• Mass of the projectile = m
• Initial speed of the projectile = u

The force due to the gravity on the particle is $F_g\ =\ mg$

And for the whole time of flight, the total vertical displacement done by the mass is zero. It only covers some horizontal displacement. The gravitational force is acting vertically downward to the particle and the vertical displacement of the particle is zero.

$\therefore W_g \=\ F_g\times d_x\ =\ 0$

Power by any force is the ratio of the work done by the force and the time taken for the whole displacement.

Now the power of the gravity = P = $\dfrac{W_g}{t}\ =\ \dfrac{0}{t}\ =\ 0$

Hence the power due to the gravity on the body is zero.