Question

A car starting from rest accelerates uniformly to acquire a speed 20 $km{h}^{-1}$ in 30 min.The distance travelled by car is this time interval will be:

(a) 600 km (b) 5 km

(c) 6 km (d) 10 km

Answer 1

Here, $u=0v=20kmpht=30min=\frac{30}{60}h=\frac{1}{2}h$

Using the first equation of motion, $v=u+at\Rightarrow 20=0+a\times \frac{1}{2}\Rightarrow a=40km/h^2$

Using the second equation of motion, $s=ut+\frac{1}{2}a{t}^2=\frac{1}{2}\times 40\times \frac{1}{2}\times \frac{1}{2}=5km$