Question

A car crashes into a wall at 60 m/s and is brought to rest in 0.1 s. Calculate the average force exerted on a 60 kg test dummy by the seat belt.

Answer 1

To solve this problem we will apply the linear motion kinematic equations, which describe the acceleration as the change of speed within a unit of time. Later we will apply the concepts related to Newton's second law to find the Force made on the object.

First we need to figure out the average acceleration:

$v_i = 60 m/s$

$v_f = 0 m/s$

$t = 0.1 s$

$m = 60kg$

Through the kinematic equations of linear motion we know that

$a = \frac{v_f-v_i}{t}$

$a = -600m/s^2$

Applying Newton's Second Law

F = ma

Where,

m = mass

a = Acceleration

Replacing

$F = (60)(600)$

$F = 36000N$

Therefore the force is 36kN