# Calculating work and force on an angle

• December 9th 2010, 08:42 AM
cheer
Calculating work and force on an angle
Example problem: A refrigerator weighing 175lbs is on a 50' ramp. The ramp has an incline of 15*. Find the magnitude of force required to keep the refrigerator from sliding down the ramp and the work required to push the refrigerator up the ramp.

The example says w=FxDcos75 so work =2265ft lbs. I dont really understand how they got this formula.

How do I find out the force to keep the fridge from sliding down the ramp?
• December 9th 2010, 08:51 AM
e^(i*pi)
To stop it sliding down the ramp you need to apply an equal, but opposite force.

$W = Fs\cos \theta$ is a standard formula (s is distance) but usually you get a flat plane so $\cos(\theta) = \cos(0) = 1$

If you draw a diagram you should be able to find the angle to be 90-15=75 degrees.

I'm just wondering how your book gets 2265, it works if F=175 but surely F=175g ?