Driving on asphalt roads entails very little rolling resistance, so most of the

Question

Driving on asphalt roads entails very little rolling resistance, so most of the energy of the engine goes to overcoming air resistance. But dr slowly in dry sand is another story If a 1200 car is driven in sand at 4.7 m/s, the coefficient of rolling friction is 0 06 In this case, nearty all of the energy that the car uses to move goes to What pr force is needed to keep the car moving forward at a constant speed? Express your answer to two significant figures and include the appropriate units Request Answer Part B What power is required for propulsion at 47 m/s? Express your answer to two significant figures and include the appropriate units. P Value Units Submit

Explanation / Answer

a) Fnet = Fprop - fr

Fprop = fr = mur m g = 0.06 * 1200 * 9.8

proplusion force = 705.6 N

b) power = Fprop * v = 705.6 * 4.7

power required = 3316 W

c) 15 miles = 24140.2 m

W = 705.6 * 24140.2 = 1.70 * 107 J

efficiency = W / E * 100 %

= (1.70 * 107 / 1.4 * 108) * 100 %

= 12.16 %

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