# Calculate the average force exerted on the driver by the seat belt

1. Dec 17, 2006

### terainfizik

1. The problem statement, all variables and given/known data
A car is involved in a collision when it is travelling at 24m/s. The driver , of mass 85kg, is brought to rest by the seat belt in a time of 400 ms . Calculate the average force exerted on the driver by the seat belt . Compare this force with his weight , and hence calculate the 'g-force' to which he's subjected by the crash, and comment on the likelihood of his sustaining serious injury.

2. Relevant equations

3. The attempt at a solution
Well, I' use F=m (v-u)/t to find the average force exerted on the driver, am I correct ? Second question , can I use formula of work done to calculate the 'g-force' ? Logically, is it impossible the 'g-force' means the potential energy stored in the car ? Guide me please .

2. Dec 17, 2006

### OlderDan

F = ma so you are on the right track with the first part. "g-force" just means the ratio of the acceleration to gravitational acceleration, which is the same as the ratio of force to weight. We commonly say a force is "7 Gs" if a force on an object is 7 times its weight.

Last edited: Dec 18, 2006
3. Dec 18, 2006

### terainfizik

'g-force' , how 'd i calculate ?

4. Dec 18, 2006

### marlon

He just explained : g force is the ratio of acceleration to gravitational acceleration.

marlon