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 driving slowly in dry sand is another story. If a 1300kg car is driven in sand at 5.2 m/s , the coefficient of rolling friction is 0.06. In this case, nearly all of the energy that the car uses to move goes to overcoming rolling friction, so you can ignore air drag in this problem.

If the car gets 15mpg when driving on sand, what is the car's efficiency? Assume the density of gasoline is 719.7kg/m^(3) .
Express your answer using two significant figures.
e=

Explanation / Answer

a similar question is solved below, but with different values. hope this helps you. Driving on an asphalt road entails very little rolling resistance, so most of the energy of the engine goes into over coming air resistance. But driving slowly in dry sand is another story. If a 1500 kg car is driven in sand at 5.0 m/s, the coe?cient of rolling friction is 0.06. In this case, nearly all the energy that the car uses to move goes to overcoming the rolling friction, so you can ignore air drag in this problem. (a) What propulsion force is needed to keep the car moving forward at a constant speed? (b) What power is required for propulsion at 5.0 m/s? (c) If the car gets 15 mpg when driving on sand, what is the car’s e?ciency? You can find the friction force that's gonna act on the car by multiplying the weight in Newtons (1500kg*9.81) by the friction coefficient. So 1500*9.81*0.6=882.9 N. So i suppose that's the answer for your first question since the car is already driven at 5 m/s the sum of the forces should be 0. And for the sum to be 0 the propulsion force should be equal to the friction force. That way when the sum of forces is zero the car isn't accelerating or decelerating (constant speed). For the other parts you just need to plug in the numbers in the formulas. For the power i think that power equals force time velocity (you should double check because it's been a long time since I've done this). So you just take the 882,9 N * 5m/s = 4414.5 N*m/s = 4414.5 kW. And for the last part, i don't remember =( sorry Hope this helps!

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