Energy Part 4: Work

Work Fake definition: Something that takes physical or mental effort. REAL definition: A force that causes a change in displacement (Δx) of an object.

Work Work is not done unless an object is moved! If I push a paperclip and it slides across a table, I’ve done work. If I apply force to a 2,000 kg boulder for 10 minutes and it doesn’t move, I’ve done NO WORK!

Work Work is only done if force and displacement are parallel. Both vectors must be E & W or N & S If force helps the motion, positive work is done. If force opposes the motion, negative work is done.

Work Work = Force x displacement W = FΔx In units: Work = Newtons x meters = (kg·m/s2)(m) = kg·m2/s2 = Joules

If a force of 48 N to the right is applied to an object and it moves 24 m, how much work was done? Δx = 24 m W = FΔx W = (48N)(24m) W = 1,152 J

W = FΔx W/F = Δx 700J/17N = Δx 41.18m = Δx If 700 J of work is done on an object as a result of 17 N of forcce being applied, how far will the object move? W = 700 J F = 17 N Δx = ? W = FΔx W/F = Δx 700J/17N = Δx 41.18m = Δx