Deck 33: Formulas for Efficiency

Question 1

For ____________________ efficiency, the output is expressed in foot-pounds of work obtained. The input is foot-pounds of work supplied.

Answer 1

mechanical

Question 2

In low gear, due to the friction of transmission gears, the brake horsepower is reduced to 65. The indicated horsepower is 100. What is the mechanical efficiency in this case?

A) 65%
B) 70%
C) 75%
D) 80%

Answer 2

65%

Question 3

One gallon of gasoline equals 125,000 Btu; 1 Btu equals 778 foot-pounds of work. One gallon of gasoline is used in pulling a load 10 miles. The force needed to pull the load is 700 pounds. What thermal efficiency does this represent? Express the answer to the nearest tenth percent.

A) 37.3%
B) 38.0%
C) 38.7%
D) 39.1%

Answer 3

38.0%

Question 4

Out of 40,000 Btu supplied, only 1,000 Btu are actually used in doing work. What is the thermal efficiency?

A) 2.5%
B) 4.5%
C) 6.5%
D) 7.5%

Question 5

For ____________________ efficiency, the output is the heat transformed into useful work. The input is the heat supplied.

Question 6

The number of British thermal units that are changed into useful work is 1,700. The number supplied is 4,300 Btu. What is the thermal efficiency to the nearest whole percent?

A) 30%
B) 35%
C) 40%
D) 45%

Question 7

____________________ horsepower means the power delivered to the driving wheels.

Question 8

The indicated horsepower is 75, but only 65 horsepower is delivered at the driving wheels. What is the mechanical efficiency? Express the answer to the nearest whole percent.

A) 68%
B) 70%
C) 75%
D) 87%

Question 9

In a car, the indicated horsepower developed by gasoline is 100. Only 88 horsepower is available for actual work. What is the mechanical efficiency?

A) 44%
B) 66%
C) 88%
D) 99%