On a ski weekend in Colorado, Bob whose mass is 75.0kg, skies downa

hill that is inclined at an angle of 15.0 degrees to thehorizontal

and has a vertical rise of 25.0m. How much work is doneby gravity

on Bob as he goes down the hill?

Answer: W = 18375J

Explanation:

Given;

Mass of bob m = 75kg

Vertical rise of plane d = 25.0m

Angle of elevation = 15°

Acceleration due to gravity = 9.8m/s2

Workdone is given by force time distance.

The workdone by gravity will be given by;

W = F*d

Where F is the weight of bob and d is the vertical distance covered by bob.

F = m*a = m*g

d = 25m

So,

W = m*g*d

W = 75 * 9.8*25

W = 18375J

Note: you may not need the angle of elevation to calculate the workdone by gravitational force.

Or we can also calculate it using

W = mgsinx * d

Where in this case d is the total length travelled on the inclined plane.

(We will still arrive at the same answer)