Question

74. A stone of mass m is thrown from earth's surface
at an angle a to the horizontal with an initial
velocity V. Ignoring the air drag, the power
developed by gravitational force t second after the
beginning of motion is
(1) mg(gt - v sina)
(2) mgv,sinat
(3) mg(g - vsinat)
(4) Zero
​

Answer 1

Answer:

It's not in the options you've provided but I want you to check twice.

Explanation:

Refer to the material.

Answer 2

Answer:

(1) mg(gt - v sina)

Explanation:

Given that

Mass = m

Angle = a

Velocity =V

The vertical component of velocity V = V sin a

As we know that acceleration due to gravity is downward and mass is moving upward so the final velocity of mass after time t given as

$V_f=V_i+at$

Vf= V - g t

Vf = V sin a - g t

We know that only vertical force is act on the mass m

F=  - m g ( negative sign means it act downward)

We know that Power

P= Force . Velocity

So here

P= F. Vf

P = - m g ( V sin a - g t)

P= m g ( g t - V sin a)

So the option a (1) is correct.

P= m g ( g t - V sin a)