Work and Kinetic Energy


by TinaMarie
Tags: energy, kinetic, work
TinaMarie
TinaMarie is offline
#1
Feb6-09, 01:09 AM
P: 2
Ok, so the question is:

A 27-pound meteorite struck a car and created a dent about 22cm deep. If the initial speed of the meteorite was 550m/s, what was the average force exerted on the meteorite by the car?

Since this question is in the work/kinetic energy chapter I assumed I'd have to use:

W = 1/2mvf2 - 1/2mvi2 to find the work done and then use the equation:

W = F*x , solving for F using W from the above equation and x = 22cm

BUT then I realized the question was asking what force did the CAR exert on the METEORITE..and that's why I'm confused. Because solving it the way I originally thought would give me the force exerted by the METEORITE on the CAR, right? So now I have no idea what to do! Any hints/suggestions would be great! Thanks!!
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LowlyPion
LowlyPion is offline
#2
Feb6-09, 01:50 AM
HW Helper
P: 5,346
What makes you think the car exerts a different force on the meteorite than it exerts on the car?
TinaMarie
TinaMarie is offline
#3
Feb6-09, 02:01 AM
P: 2
I don't really know what made me assume that.. but it just makes sense that the car would exert a greater force on the meteorite, otherwise the meteorite wouldn't have stopped (aka if the meteorite's force was larger than the car's force, then wouldn't the meteorite just slam right through the car?) Kind of like the whole, while I'm sitting on my couch my weight is exerting a force on the couch, but the couch is extering a normal force back on me. If my weight exerted a force greater than the couch's normal force then I'd fall through the couch - ie: the meteorite's force must be greater than the car's force because the meteorite pushes through the car some.


Ok, now I've contradicted myself in my own post! Oi.. I hate physics! I've just confused myself even more! But.. I guess it makes sense that both forces would be equal, because the meteorite does stop.. I'm just curious if they're equal then why does the meteorite make a dent at all?

UGH!!


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