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1) Estimate the maximum speed of a horse.
Assume the horse is 1.8 m tall and 0.5m
wide.
By definition the power output of a horse is 1hp = 746 W.
At constant max speed
F
net
= 0.
The propulsion force is balanced by the drag of air resistance D = 0.5 C
r
Av
2
,
where C ≈ 1,
r
= 1kg/m
3
, A = (1.8m)(.5m) = 0.9m
2
P = 746 W = Fv = Dv = .5Av
3
v = [2(746)/0.9]
1/3
= 12m/s = (27mph)
2) In a hydroelectric dam, water falls 25 m and then spins a turbine to generate electricity.
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Unformatted text preview: a. What is D U of 1.0 kg of water? b. Suppose the dam is 80% efficient at converting the water's potential energy to electrical energy. How many kilograms of water must pass through the turbines each second to generate 50 MW of electricity? This is a typical value for a small hydroelectric dam. ....
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This note was uploaded on 05/20/2008 for the course PHYS 161 taught by Professor Hammer during the Spring '07 term at Maryland.
 Spring '07
 Hammer
 mechanics, Resistance, Force, Power

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