Estimate the work you do to mow a lawn 10 m by 20 m with a 50-cm-wide mower. Assume you push with a force of about 15 N.

VIDEO TRANSCRIPT

This is Giancoli Answers with Mr. Dychko. To figure out the work done in mowing a lawn, we are gonna multiply the force applied in the lawn mower, which, we just have to assume, is parallel to the lawnmower's displacement, which isn't exactly gonna be true coz the lawnmower's gonna be on some angle like this probably and it'll be pushing down into the right. But nevertheless, we are just making an estimate. So we just have this 15 newtons multiplied by the distance that we push the mower. So the distance the mower goes is the part that requires a bit of work. And the mower is 50 centimeters wide, which is 0.50 meters and we have to mow this rectangle. So the total distance that you will walk will be the well, you have to go up, one swath here; we'll take out this 50 centimeter wide swath and then come back down again this way and go back up again this way and how many swaths are needed to mow this whole thing and that will be 20 meters times 1 swath for every 0.5 meters, makes you have to go up and down 40 times, 40 swaths. But that's not going to be the total distance coz when you get to the end of a swath, you are gonna be, sort of, turning and pushing the more this way and then going back down. And the total distance you have to go to the right here, is gonna be, 20 meters and so we'll have, the 40 swaths walked vertically and then the 20 meters to the right is gonna be the total distance. And so the 40 swaths is gonna be 10 meters in length for each one. So that gives 400 meters plus the 20 meters, straight to the right, gives 420 meters. So 15 newtons times 420 meters is 6300 joules.