Question

27. Each piston of an engine makes a sharp sound every other revolution of the engine. (a) How fast is a race car going if its eight-cylinder engine emits a sound of frequency 750 Hz, given that the engine makes 2000 revolutions per kilometer? (b) At how many revolutions per minute is the engine rotating?

Answer 1

a)V= 93.75 m/s

b)The number of revolution per minute = 11,250 rev/min

Step-by-step explanation:

Given that

Number piston , n =8

Frequency ,f= 750 Hz

Revolution(R) = 2000 revolutions per kilometer

frequency of each piston

f'=f/n

f'=750/8

f'=93.75 Hz

So the number of revolution made by piston(r) = 2 x 93.75 rev/s

number of revolution made by piston(r) = 187.5 rev/s

The number of revolution per minute = 187.5 x 60 rev/min

The number of revolution per minute = 11,250 rev/min

So the speed of car V given as

`V=(r)/(R)`

r =number of revolution per second

R = revolutions per kilometer

`V=(187.5)/(2000* 10^(-3))`

V= 93.75 m/s