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December 18, 2014

December 18, 2014

Posted by **Lars** on Sunday, November 12, 2006 at 10:29am.

I changed 65 cm into .00065 km. I think i need to use F=ma so I need to find a. To find a I used d =1/2 (v0+v)t to find time and I got 2.45X10^-5. then I used a = v/t and i got 2163265.31 as a. Then i pluged m and a into F=ma and I got 88693877.71 for the answer. Is this correct? I wouldn't think the force would be this high.

Why not use

force*distance= 1/2 mass*velocity^2

That is the work done on the bag is equal to the change in KE of the passenger.

You should get the same answer as your technique, but I suspect the teacher was exploring the energy relationships in motion, as I laid out.

For information:

force*distance= 1/2 mass*velocity^2

force*distance= 1/2 mass*(avgveloctity*2)^2

force*distance= 2 mass*(avgveloctity )^2

force*avgvelociy*time= 2 mass*(avgveloctity )^2

force = 2 mass*(avgveloctity )/time

force = mass*(2avgveloctity )/time

force= mass*acceleration as you started from.

- physics -
**Robert**, Sunday, October 14, 2007 at 3:20pmMust use meters, not kilometers.

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