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March, 2024

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This is a physics problem, sorry but like a 3rd grader should be able to get it and I can't see why it is wrong

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chicken
Posts: 6843 - Karma: 2,122
Two objects with masses 4.00kg and 1.80kg hang 0.500m above the floor from the ends of a cord 7.30m long passing over a frictionless pulley. Both objects start from rest.

what is the maximum height reached by the 1.8kg block?

ok so isn't it just that the 4.0 kg block will obviously go down until it hits the floor, which is 0.5 m away? well if they are connected by a pully, then that should pull the 1.8 kg up .5m, making its final (and highest height) 1m

well apparantly that is not the answer.
Oct 7 2010 1:08AM
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chicken
Posts: 6843 - Karma: 2,122
ok nvm mods can you delete this thread, sorry for brining physics to NS wont happen again
Oct 7 2010 1:14AM
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cooper.fry
Posts: 2229 - Karma: 34

I see what you were thinking, but the real answer is below.

Click for larger image

Oct 7 2010 1:18AM
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JWoods
Posts: 2369 - Karma: 2,635
Crazy shit, im doing this in calc right now
Oct 7 2010 1:20AM
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COskier
Posts: 1066 - Karma: 131
Sounds like you are using an online hw thing. Did you use 3 sig figs?
Oct 7 2010 1:27AM
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cooper.fry
Posts: 2229 - Karma: 34
damn, ha i just typed in long math problem on google images
Oct 7 2010 1:27AM
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smooticus
Posts: 1798 - Karma: 27
i hate online homework soooo damn much. At first i thought it would be super convenient, but i have never been so close to breaking my computer. There super picky about there answers and it so easy to make a insignificant mistake. Plus my dorm doesnt have wifi so i have to sit at my desk for fucking hours everyday
Oct 7 2010 1:42AM
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chicken
Posts: 6843 - Karma: 2,122
tell me about it. mastering physics sucks so bad. I loose 10%-20% on each assignment due to formatting issues. They should give you like 3 chances before it takes any marks off
Oct 7 2010 3:23PM
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7-3instacall
Posts: 999 - Karma: 1,005
dude can we know the answer? cause i cant believe its not 1 m
Oct 7 2010 3:47PM
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applejuice.
Posts: 5506 - Karma: 1,512
DERIVATIVES YAY!
Oct 7 2010 3:48PM
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gregorio
Posts: 2372 - Karma: 151
WOOOOO
Oct 7 2010 3:51PM
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rudager
Posts: 11332 - Karma: 4,597
42



Online homework blows. Online tests are sweet, all open book.
Oct 7 2010 3:54PM
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chicken
Posts: 6843 - Karma: 2,122
1.19m because when mass 1 hits the ground, mass 2 still has upwards velocity.

I guess that's why you use math and science to do physics, and not logic.
Oct 7 2010 4:34PM
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flexpattern
Posts: 1090 - Karma: 45
mastering physics!!! I hate that so much! my uni loves it and all the students hate it... it takes so long to input answers and they are nearly always wrongly formatted,....
Oct 7 2010 4:45PM
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DERS.
Posts: 6299 - Karma: 1,293
ahah this isnt that hard.. i remember when all this shit looked sooooooo complicated
Oct 7 2010 4:47PM
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7-3instacall
Posts: 999 - Karma: 1,005
oh right, ...schoolsucks
Oct 7 2010 4:53PM
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chapz
Posts: 10182 - Karma: 66
this.
Oct 7 2010 5:18PM
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ECMike
Posts: 33 - Karma: 22
Yeah I got 1.20753 using g= 10m/s^2. Basically find the acceleration upwards by taking the difference of the tension in the string(from the other mass) and the force of gravity. Then find the time it takes for the mass to fall(or the other mass to reach 1m). Find the velocity of the 1.8 kg ball at this point( this is vo for the next equation). From then on the 1.8 kg mass is a projectile. Find the equation for y. To find the time until it reaches its peak I derived this and solved for dy/dt=0. Take this time and plug it into your equation for y. Easy... haha not really.

equations:
ma = T - mg
y = 0 + 0 + 1/2*(a)*t^2
v = vo + at
y = yo + vo*t - 1/2*(g)*t^2
y = 1.20753 m.
Oct 7 2010 7:24PM
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tommyp1ckles
Posts: 1337 - Karma: 55
omg i know, i have to do my calc class work online and ill get the answer in two minutes and spend 10 minutes trying to enter it without making a mistake typing in the answer.
Oct 7 2010 7:36PM
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