A man pushes a lawn mower with a 40 N force directed at a angle of 20° downward from the horizontal. Find the work done by the man as he cuts a strip of grass 20 m long. 

(Ans: 7.5 ｘ 10² J)



Given:

Force = F = 10 N

Angle = θ = 20°

Length of the strip of the grass =  d = 20 m   


To Find:

Work done =  W = ?   


Solution:

Formula for work done

W = `\vec F` . `\vec d`

W = F d cos θ

Putting values

W = 40 N ｘ 20 m ｘ cos 20°

W = 800 N m ｘ 0.940

W = 751.75 N m 

Or

W = 7.5 ｘ 10² J -----------Ans.



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