Question

Each piston of an engine makes a sharp sound every other revolution of the engine. 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?

Answer 1

Answer:

93.75 m/s

Explanation:

Given:

The frequency of the sound = 750 Hz

The number of pistons making the sound = 8

Revolutions made by the engine = 2000 revolutions/ km

Thus,

the frequency of sound by 1 piston = 750 / 8  = 93.75 Hz

also, it is given that for every other revolution sound is made.

thus, for every 2 revolution sound is made

therefore,

Number of revolutions per second = 93.75 Hz × 2 = 187.5 rev/s

Now,

the speed of the car will be calculated as:

= Number of revolutions per second / Revolutions made by the engine

or

The speed of the car = $\frac{187.5\ rev/s}{2000\ rev/km}$

or

The speed of the car = 0.09375 km/s = 93.75 m/s