Question

200 kg car traveling at 10 m/s hits a tree and is brought to rest in 0.10s. What is the magnitude of the average force acting on the car to bring it to rest?

Answer 1

mass = 200 kg

initial speed, u = 10 m/s

final speed , v = 0

time ,t = 0.10 s

acceleration , a = ?

$using \: \: v = u + at \\ \\ = > a = \frac{0 - 10}{0.10} \\ \\ = > a = - 100 \: m{s}^{ - 1} \\ \\ force = mass \: \times \: acceleration \\ \\ = 200 \times ( 100) \\ \\ = 20000 \: N \\ \\ = 2 \times {10}^{4} N$

(here acceleration is -ve means it is retarding acceleration)