Question

A car breaks from a speed of 108km/h to 72km/h during a displacement of 100m, what is its aceleration ?​

Answer 1

First, note that 100 m = 0.100 km.

Recall that

v² - u² = 2 a ∆x

where u and v are initial and final velocities; a is acceleration; and ∆x is displacement. Solve for a :

(72 km/h)² - (108 km/h)² = 2 a (0.100 km)

a = ((72 km/h)² - (108 km/h)²) / (0.200 km)

a = -32,400 km/h²

If you want to convert this to m/s², we have

(-32,400 km/h²) = (-32,400 km/h²) (1000 m/km) (1/3600 h/s)²

(-32,400 km/h²) = -2.50 m/s²