# Suppose a car travels 108 km at a speed of 30.0 m/s, and uses 2.20 gallons of gasoline. Only 30% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. (The energy content of gasoline is 1.3 ✕ 108 J per gallon.)  a) What is the force exerted to keep the car moving at constant speed? N (b) If the required force is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of 28.0 m/s? gallons

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Suppose a car travels 108 km at a speed of 30.0 m/s, and uses 2.20 gallons of gasoline. Only 30% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. (The energy content of gasoline is 1.3 ✕ 108 J per gallon.)

1. a) What is the force exerted to keep the car moving at constant speed?

(b) If the required force is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of 28.0 m/s?
gallons
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Step 1

(A)The number of gallons of gasoline is 2.20.

The percentage of gasoline goes into useful work is 30%.

Energy content of a gasoline is 1.3x108J per gallon.

Thus the energy used by the car is.

Step 2

Write the expression for work done.

Step 3

Rewrite equation (I) to obtain an expression for...

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### Kinematics 