Momentum Review: Force & Time for Rhonda's Brakes/Windshield

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SUMMARY

The discussion centers on calculating the average force exerted on Rhonda, a 60.0 kg driver, during a sudden stop in her sports car traveling at 25.0 m/s. When wearing a seat belt, the average force exerted on her body is determined using the formula F = Δp/Δt, where Δp represents the change in momentum and Δt is the time taken to stop, which is 0.400 seconds. In contrast, if she were not wearing a seat belt and her head hit the windshield, stopping in 1.0 x 10-3 seconds, a different average force would be calculated. The discussion highlights the importance of understanding momentum and force in collision scenarios.

PREREQUISITES
  • Understanding of momentum (P = mv)
  • Knowledge of Newton's second law (F = ma)
  • Familiarity with the concept of impulse (Δp = FΔt)
  • Basic algebra for manipulating equations
NEXT STEPS
  • Research the relationship between force, mass, and acceleration using Newton's laws.
  • Learn about impulse and its application in collision analysis.
  • Explore real-world applications of momentum conservation in automotive safety.
  • Study examples of calculating forces in different collision scenarios.
USEFUL FOR

This discussion is beneficial for physics students, automotive safety engineers, and anyone interested in understanding the dynamics of force and momentum in collision situations.

andthismeans
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Homework Statement


Rhonda, who has a mass of 60.0 kg, is riding at 25.0 m/s in her sports car when she suddenly slams on the brakes to avoid hitting a dog crossing the road. She is wearing her seat belt, which brings her body to a stop in 0.400s. What average force did the seat belt exert on her body? If she had not been wearing her seat belt, and the windshield had stopped her head in 1.0 X 10-3s, what average force would the windshield have exerted on her?

Homework Equations


The only ones I know is Pi = Pf
[mv1i + mv2i = mv1f + mv2f] <---I don't know this as well
P = momentum i = initial f = final 1 = mass of first object 2 = mass of second object

The Attempt at a Solution


I don't know where force and time come in so I don't know how to start/finish it. Do I need another formula. If so, that's all the information I would need.
 
Last edited:
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Welcome to PF.

Consider that Force can also be expressed as the change in momentum (p) divided by the time over which it changes.

F = ma = Δp/Δt
 

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