Question

A car increases its speed from 20km/hr to 50km/hr in seconds. Its acceleration is _____.
a) 30 m/s2 b) 3 m/s2 c) 18 m/s2 d) 0.83 m/s2 6

Answer 1

Answer:

Option D

0.83 m/s2

Explanation:

Time is assumed as 10 seconds

First, convert the speeds from km/h to m/s

20 km/h\times \frac {1000 m}{3600 s}=5.555555556 m/s \approx 5.56 m/s

50 km/h\times \frac {1000 m}{3600 s}=13.88888889  m/s \approx 13.89 m/s

Acceleration, $a=\frac {v-u}{t}$ where u and v are the initial and final velocities respectively, t is the time taken to accelerate.

Substituting 13.89 m/s for v, 5.56 m/s for u and 10 s for t then

$a=\frac {13.89-5.56}{10}=0.8333333 m/s^{2}\approx 0.83 m/s^{2}$