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A man pushes a lawnmower 50ft in 5s exerting a force of 30Ib at an angle of 53 degrees with the horizon Find the work done and the average power expended in horsepower?
Wiki User
∙ 14y ago
Work is defined as the product of a force acting through a distance (parallel to it). Power is the rate of work being done per second.
W = F * d
(that notation just means "parallel", and the two are being multiplied).
Since our force isn't totally parallel to his motion already, we have to only use the component of it that IS parallel. That component is "F*cos(53˚)" (assuming he is pushing the mower parallel to "the horizontal").
F = F*cos(53˚) lb
F = 30lb*cos(53˚) lb
F = 18.05 lb
(approx.)
Now that we've found F, multiply it by the distance through which he pushes it.
W = F * d ftlb
F = 18.05 lb
d = 50ft
W = 902.72 ftlb
This is work done. Average power is the work done over the time elapsed:
P = W/Δt
P = 902.72 ftlb / 5s
P = 180.54 ftlb/s
To convert to horsepower, we use the conversion equation
1hp = 550ftlb/s
P = 180.54/550 hp
P = 0.33 hp
(approx.)
Wiki User
∙ 14y ago
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A person of mass 75 kg runs to the top of a building 45 m high in 2 min What is the average power expended?
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