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1-D kinematic Problem

  • Thread starter bond535
  • Start date
  • #1
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Homework Statement


Determine the average number of g's experienced by someone abruptly coming to rest from an initial velocity of 30mph (such as in a car crash). Take the distance involved in coming to rest to be 1 m.

Homework Equations


V=Vo+at
ΔS=VoT+1/2at^2
V^2=Vo^2+2aΔS

The Attempt at a Solution


t=?
a=?
Vo= 30 mph
V=?
ΔS=?

Thank you, I'm really stuck and any help will be deeply appreciate it.
 

Answers and Replies

  • #2
lewando
Homework Helper
Gold Member
1,349
135
You know Vfinal = 0 and ΔS (change in distance) = 1m. does that help?
 
  • #3
2
0
so...
t=?
a=?
Vo= 30 mph
V=0
ΔS=1m

V^2=Vo^2+2aΔS
0=(30mph)^2+2a(1m)
which resulted in a= -450mph

I know g= 9.8m/s ... so I'm assuming I have to change the -450mph to m/s by diving -450/3600s = 0.125m/s

I really dont know what to do next or if I'm in the right track...
 
  • #4
lewando
Homework Helper
Gold Member
1,349
135
V^2=Vo^2+2aΔS
0=(30mph)^2+2a(1m)
which resulted in a= -450mph
a should be in units of m/s2

(convert mph to m/s)
 

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