First, note that 100 m = 0.100 km.
Recall that
<em>v</em>² - <em>u</em>² = 2 <em>a</em> ∆<em>x</em>
where <em>u</em> and <em>v</em> are initial and final velocities; <em>a</em> is acceleration; and ∆<em>x</em> is displacement. Solve for <em>a</em> :
(72 km/h)² - (108 km/h)² = 2 <em>a</em> (0.100 km)
<em>a</em> = ((72 km/h)² - (108 km/h)²) / (0.200 km)
<em>a</em> = -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
