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holly
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Physics class is starting to sound like advertisements for toiletries: Men, try "Momentum!" Ladies, wear "Impulse" or "Joules," enriched with pheremones! Ha ha
Having trouble with this problem, about a bungee jumper jumping off a cliff for 5 seconds total, in free fall for 3 seconds, then slowing and stopping in the last two seconds of his fall. He weighs 100 kg. Okay, I got his momentum for the third second, p=mv, meaning 3000kg m/s...
But, then I'm asked what is the impulse during the 2-s interval of slowing down? The answer is given as 1500N, but I can't get that using the formulas I have. My formula for impulse says F times t = impulse. Okay, I go try to find F by finding acceleration (because F=ma?), which I thought was 10m/s/s but another formula says no, get acc by a=Delta v divided by t interval of change...by using that, I put 30-0 to get the change of velocity, then divide that by the 2 second time interval, giving me 15. Then I find F by using 15 times 100kg (his weight). Then, going back to the other equation, I put 1500 times 2 seconds, and get 3000N. Wrong, it's supposed to be 1500! If I put average velocity in the a=deltav/t equation, and I get 7.5 and then it all works out, but am I supposed to be taking an average velocity? Can someone help me, THERE ARE TOO MANY EQUATIONS and I can't understand which to use!
I don't know any calculus, I don't know the symbols usually used, either, so please dumb it down for me.
Thanking you in advance...
Having trouble with this problem, about a bungee jumper jumping off a cliff for 5 seconds total, in free fall for 3 seconds, then slowing and stopping in the last two seconds of his fall. He weighs 100 kg. Okay, I got his momentum for the third second, p=mv, meaning 3000kg m/s...
But, then I'm asked what is the impulse during the 2-s interval of slowing down? The answer is given as 1500N, but I can't get that using the formulas I have. My formula for impulse says F times t = impulse. Okay, I go try to find F by finding acceleration (because F=ma?), which I thought was 10m/s/s but another formula says no, get acc by a=Delta v divided by t interval of change...by using that, I put 30-0 to get the change of velocity, then divide that by the 2 second time interval, giving me 15. Then I find F by using 15 times 100kg (his weight). Then, going back to the other equation, I put 1500 times 2 seconds, and get 3000N. Wrong, it's supposed to be 1500! If I put average velocity in the a=deltav/t equation, and I get 7.5 and then it all works out, but am I supposed to be taking an average velocity? Can someone help me, THERE ARE TOO MANY EQUATIONS and I can't understand which to use!
I don't know any calculus, I don't know the symbols usually used, either, so please dumb it down for me.
Thanking you in advance...
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