Calculating Momentum Change of 70kg Passenger in Car Crash

AI Thread Summary
The discussion focuses on calculating the change of momentum for a 70 kg passenger in a car crash, where the car decelerates from 24 m/s to rest in 0.4 seconds. The change of momentum is correctly calculated as 1680 kg m/s using the formula mΔv. Participants confirm that impulse can be calculated using either FΔt or mΔv, depending on the available information. They emphasize the importance of analyzing the given data in exam questions to determine which equation to use. Overall, understanding the interchangeability of these formulas is crucial for solving physics problems related to momentum and impulse.
cstatepat
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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?
 
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welcome to pf!

hi cstatepat! welcome to pf! :wink:
cstatepat said:
Am I calculating this right?

yes :smile:
Is FΔt=mΔv interchangeable depending on the given information?

not following you :confused:

∫ F dt is impulse …

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


tiny-tim said:
hi cstatepat! welcome to pf! :wink:


yes :smile:


not following you :confused:

∫ F dt is impulse …

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

Thank you for the warm welcome! :biggrin:

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.
 
cstatepat said:
For example the question I asked didn't have a given for F so therefore I would try to find the impulse using mΔv.

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! :wink:
 

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