Reducing Hip Fracture Risk with Elastic Hip Pads: What Acceleration is Needed?

[maff is tuff]

Homework Statement

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?

Homework Equations

v^2 = v0^2 + 2a(x-x0)

The Attempt at a Solution

My attempt is attached below. Thanks everybody for the help :)

 

[nayfie]

Does it compress to 2cm or by 2cm?

 

[maff is tuff]

Oh it says by. So you're sayin my (x-x0) should be .02 not .03.

 

[nayfie]

Correct :)

 

[maff is tuff]

Yep that was the problem. Thanks man you've been helping me all day.