Question

A car’s tachometer indicates the angular velocity of the engine’s crankshaft in rpm. A car stopped

at a traffic light has its engine idling at 500 rpm. When the light turns green, the crankshaft

rotation speeds up at a constant rate to 2500 rpm in a time interval of 3.0 s. How many

revolutions does the crankshaft make in these time interval?

Answer 1

Given:

$n_1=500\:\rm rpm$

$n_2=2500\:\rm rpm$

$t=3.0\:\rm s$

The number of revolution

$$N=\frac{n_1+n_2}{2}t=\frac{500+2500}{2}*3.0=4500$$