The human body can survive an acceleration of less than 250 m/s2. If a person is involved in a car accident with an initial speed of 120 km/hr and is protected by an airbag, over what distance must the airbag function in order for the person to survive the crash?

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What formulas am i going to use? Help me please. Or can someone give me an explanation? Thank u very much

Question

The human body can survive an acceleration of less than 250 m/s2. If a person is involved in a car accident with an initial speed of 120 km/hr and is protected by an airbag, over what distance must the airbag function in order for the person to survive the crash?

_
What formulas am i going to use? Help me please. Or can someone give me an explanation? Thank u very much

zephyr141 · Answer

use kinematics$$v^2=v_0^2+2ad$$solve for d. final velocity is going to be zero. initial velocity is given and d is given.

zephyr141 · Answer

oh right. you might have to do some conversions from kilometers to meters

zephyr141 · Answer

and hours to seconds.

anonymous · Answer

@zephyr141 yea so i got 33.33 m/s, plus i substituted it to the equation, 
 
Vo = 120 km/hr = 33.33 m/s
Vf = 0 m/s
a = 250 m/s^2

Vf^2 = Vo^2 + 2ad

d = (Vf^2-Vo^2)/2a

i calculated d, and i got -2.22 m

zephyr141 · Answer

the person is slowing down. what makes a person slow down? a negative acceleration. so put in a negative sign there and you'll get the same thing but positive.

anonymous · Answer

@zephyr141 ah!! that!! yes okay, 2.22m :) got it, thanks!!

zephyr141 · Answer

nice!|dw:1418547809535:dw|