# Calculating change in momemtum , impulse, and average force of a person in a car.

1. Feb 27, 2012

### cstatepat

1.A 70 kg front seat passenger is in a car moving initially at 24m/s and is brought to rest by an airbag in 0.4 seconds after a crash.

2. What is the change of momentum of the person in the car

3. mΔv = (70kg)(24m/s) = 1680kg m/s

Am I calculating this right? Is FΔt=mΔv interchangeable depending on the given information?

2. Feb 27, 2012

### tiny-tim

welcome to pf!

hi cstatepat! welcome to pf!
yes
not following you

∫ F dt is impulse

if F is constant, that's the same as F∆t​

3. Feb 27, 2012

### cstatepat

Re: welcome to pf!

Thank you for the warm welcome!

What I am trying to say is if I am trying to calculate the impulse and I look at my equations FΔt or mΔv based on the information the questions gives me I can use either equation to calculate impulse? For example the question I asked didn't have a given for F so therefore I would try to find the impulse using mΔv.

4. Feb 27, 2012

### tiny-tim

oh i see!

yes, exam questions do that …

sometimes they give you the data for one side of an equation, sometimes the other side …

you have to look at what they give you, and work with that!