- #1

Lori

## Homework Statement

At what rate is the gravitational force doing work on a 2.0 kg projectile at an instant when the velocity of the projectile is 4.0 m/s directed 30 degrees above the horizontal.

**the answer is -39 W but i need help on why!**

## Homework Equations

P = W/T

Power = Work*V

=Force*cos(theta)*V

## The Attempt at a Solution

I know that the force of the gravity is just 9.8*2, but why is the angle that i plug in cos(120) ? I'm not sure why/how we use angle of 120 as oppose to 90-30 = 60 degrees...

If you can provide a sketch for me visually, it would help a lot...

Here's what i thought: