# Free Fall Acceleration Problem

1. Sep 8, 2008

### tater08

1. The problem statement, all variables and given/known data
Falls resulting in hip fractures are a major cause of injury and even death to the elderly. Typically, the hip’s speed at impact is about 2.0 m/s. If this can be reduced to 1.3 m/s or less, the hip will usually not fracture. One way to do this is by wearing elastic hip pads.

If a typical pad is 5.0 cm thick and compresses by 2.0 cm during the impact of a fall, what acceleration (in m/s^2) does the hip undergo to reduce its speed to 1.3 m/s?

2. Relevant equations
(y1-y0)=(Vf^2-V0^2)/2a

3. The attempt at a solution
y1-yO=-2 cm = 0.02M Vf= 1.3 V0=2.0 a=?
1.3^2-2.0^2 =-2.31

(-2.31m^2/s^2)/ 2*-0.02m =a a= 57.75m/s^2

question is......did i do this problem right because this is an online hw problem and i keep getting it wrong so i'm wondering if it is the program or if it just me.

thanks

2. Sep 9, 2008

### tiny-tim

Hi tater08!

I think it must be a misprint …

hmm … try using 3.0 cm instead of 2.0 cm, and see if the computer accepts that!