Question

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

(a) How fast (in km/hr) is a race car going if its eight-cylinder engine emits a sound of frequency 543 Hz, given that the engine makes 2022 revolutions per kilometer?
(b) At how many revolutions per minute is the engine rotating?

Answer 1

Answer:

a) v = 241.69 $\frac{km}{h}$

b) w = 8145 $\frac{rev}{min}$

Explanation:

Knowing  $\frac{1}{2022} \frac{km}{rev}$ and 1 rev = 4 sounds

$w = 543 \frac{sounds}{s} * \frac{1 rev}{ 4 sounds}\\ w = 135.75 \frac{rev}{s}\\ v = \frac{1}{2022} \frac{km}{s} * 135.75 \frac{rev}{s} * \frac{3600 s}{1 h} \\v = 241.69 \frac{km}{h} \\w = 135.75 \frac{rev}{s} * \frac{60 s}{1 min}\\ w = 8145 \frac{rev}{min}$