A body of mass 2 kg is projected at 20 m/s at an angle 60° above the horizontal. Power due to the gravitational force at its highest point is

Question

A body of mass 2 kg is projected at 20 m/s at an angle 60° above the horizontal. Power due to the gravitational force at its highest point is (A)  200 W  (B)  100√3 W  (C)  50 W  (D) zero

Tardigrade Admin · Accepted Answer

Velocity of the highest point, V x = V cos θ=20 × cos 60° =20 × (1/2)=10 m / s Now the angle between the horizontal velocity and the gravitational force θ=90° Power = fv cos θ= mgv cos 90°=0 (Since cos 90°=0 )

Q. A body of mass $2 k g$ is projected at $20 m / s$ at an angle $6 0^{\circ}$ above the horizontal. Power due to the gravitational force at its highest point is

$200 W$

$1003 W$

$50 W$

zero

Velocity of the highest point,
$V_{x} = V cos θ = 20 \times cos 6 0^{\circ}$
$= 20 \times \frac{1}{2} = 10 m / s$
Now the angle between the horizontal velocity and the gravitational force $θ = 9 0^{\circ}$
Power $= f v cos θ = m gv cos 9 0^{\circ} = 0$
(Since $cos 9 0^{\circ} = 0$ )

Q. A body of mass 2kg is projected at 20m/s at an angle 60∘ above the horizontal. Power due to the gravitational force at its highest point is

200W

1003​W

50W