The tutor reflects on the amount of work done raking.

From a physics point of view,

Work=ForcexDistance

or just

W=Fd

Today, out raking, I had to break up the weedy ground of the bark mulch. I’d estimate, on average, the force behind my rake strokes was 15lb. Physics uses Newtons; 2.2lb=9.8N. Therefore, 1lb=(9.8/2.2)N=4.45N; furthermore, 15lb=66.8N

I’d say my average rake stroke had length 15cm=0.15m.

Therefore, the average rake stroke accomplished work as follows:

W=Fd=(66.8)(0.15)=10.J

I spent 90 minutes raking. I’d estimate, on average, 15 rake strokes per minute. (Some minutes I did a lot more, but many minutes I didn’t do any.) My total rake strokes would therefore be 90×15=1350.

My total work raking, estimated, is 1350(10)=13500J or 13.5kJ.

In a coming post I’ll bring that number into further perspective:)

Source:

Heath, Robert W. et al. Fundamentals of Physics. D.C. Heath Canada Ltd, 1981.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.