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As punishment, Zeus banished him to Hades, where he was doomed for eternity to roll a rock up hill, only to have it roll back on him. If Sisyphus stands in front of a 400 lbs spherical rock on a 20 degres incline, then what force applied in the direction of the incline would keep the rock from rolling down the incline.

Jan 24, 2019
edited by Guest  Jan 24, 2019

$$\text{If you draw the force diagram you see that the gravitational force on the rock}\\ \text{can be broken up into a component normal to the inclined ground and a component }\\ \text{along the direction of potential motion}. \text{The magnitude of the component along the direction of potential motion is}\\ |f_m| = 400 \sin(20^\circ) \approx 136.8~ lbs\\ \text{This is the force that must be applied to the rock in the direction of the incline}$$