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# mechanics 2 Watch

1. so ive just started learning m2 buy my teacher is awful, shes given us a few question but i have no clue what to do

a ball mass 0.4kg is fired horizontally 350m/s. it hits a target penetrating for 0.25m before coming to rest, using the work energy principle find the resistive force of the target
2. well you need to let the kinetic energy of the ball equal the work done against the resistance of the target

KE = .5mv2

work done = Force * Distance
3. (Original post by the bear)
well you need to let the kinetic energy of the ball equal the work done against the resistance of the target

KE = .5mv2

work done = Force * Distance

how do i get the force of this? 'f=ma' i dont know acceleration

edit
do i do 245000=f x 0.25
4. (Original post by printergirl)
edit
do i do 245000=f x 0.25
yes
5. (Original post by TenOfThem)
yes
so answer is 98000 N, this seems very large!
6. (Original post by printergirl)
so answer is 98000 N, this seems very large!
Well

It was going very fast

And it did have to stop pretty quickly

So a big force would be needed
7. 350 m/s is 790 miles per hour....

Jumbo Jets cruise at 250 m/s

none of the Fighter Planes in WWII exceeded 690 miles per hour:

http://www.militaryfactory.com/aircr...d-by-speed.asp

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