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Forces (Newton's Law) Help 
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#1
Sep2606, 08:53 PM

P: 190

Well, I am having trouble with this and I been looking at the book for a long time and still lost. The teacher never went over this so no notes to help me out here either.
A football punter accelerates a football from rest to a speed of 10 m/s during the time in which his toe is in contact with the ball (about 0.18 s). If the football has a mass of 0.50 kg, what average force does the punter exert on the ball? N I have no slight clue on where to start or what formula I should be using. Any help would be great. 


#2
Sep2606, 09:07 PM

P: 62

I think that means the football's starting speed is 10m/s which is the time the football punter kick it!



#3
Sep2606, 09:15 PM

P: 190

edit: okay i figure out how to do the first one but at a lost on this problem
A freight train has a mass of 1.3 x 10^7 kg. If the locomotive can exert a constant pull of 6.8 x 10^5 N, how long does it take to increase the speed of the train from rest to 84 km/h? min so far i got this part from reading the book ma = F_net > a = F_net/m = 6.8 x 10^5 N/1.3 x 10^7 kg = .052 m/s^2 84km/h x .278 I think i use v = at + V_0 = (.052)t = 23.352 t = 449 second edit: okay nevermind i figure this out do to my own mistake. I got the wrong conversion for km/h to m/s. I done correction to it. 


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