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Bushviper
Joined: 07 Aug 2006 Posts: 281

Posted: Tue Feb 17, 2009 3:03 pm Post subject: Physics 


Hey I know this isn't the type of thing you expect to see on the ML forums but I need some help with 2 problems of my physics homework. There has to be someone on ML that knows how to solve these.
Blocks with masses of 1.0 Kg, 2.0 Kg, and 3.0 Kg are lined up in a row on a frictionless table. All three are pushed forward by a 12 N force applied to the 1.0 Kg block. How much force does the 2.0 Kg block exert on:
A) The 3.0 Kg block
B) The 1.0 Kg block
A 2.0 m long, 500 Kg rope pulls a 10 Kg block of ice across a horizontal, frictionless surface. The block accelerates at 2.0 m/s2. How much force pulls forward on:
A) The block of ice
B) The rope
Any help would be appreciated. Thanks. 

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Badden
Joined: 08 Feb 2009 Posts: 5

Posted: Tue Feb 17, 2009 3:14 pm Post subject: 


force = mass times acceleration
newton's 2nd law 

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Bushviper
Joined: 07 Aug 2006 Posts: 281

Posted: Tue Feb 17, 2009 3:38 pm Post subject: 


I know that but how would you apply it to either problem or at least how would you set it up? 

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Badden
Joined: 08 Feb 2009 Posts: 5


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Sprouts
Joined: 15 Feb 2006 Posts: 101

Posted: Tue Feb 17, 2009 7:08 pm Post subject: 


this is so easy... 

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ik Level 1 Judge
Joined: 11 Sep 2007 Posts: 335

Posted: Tue Feb 17, 2009 7:15 pm Post subject: 


No using ML for help on your science homework ^^ 

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CoLd
Joined: 11 Feb 2009 Posts: 7

Posted: Tue Feb 17, 2009 9:36 pm Post subject: 


losers... 

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Rosie
Joined: 29 Feb 2008 Posts: 14

Posted: Wed Feb 18, 2009 1:01 am Post subject: Re: Physics 


Bushviper wrote: 
Blocks with masses of 1.0 Kg, 2.0 Kg, and 3.0 Kg are lined up in a row on a frictionless table. All three are pushed forward by a 12 N force applied to the 1.0 Kg block. How much force does the 2.0 Kg block exert on:
A) The 3.0 Kg block
B) The 1.0 Kg block

You can figure out acceleration by treaint all of them as a single block.
so you get 6kg.
F=ma
12=6 (2m/s^2).
so 2 is your a.
Ok so draw out your force diagrams.
All three should have gravity and normal forces. so im not gunna list those. From this you can figure out trivial answers.
MA <(1.0)> 12 N
Ok so we know the force that block 2 exerts on block 1 is 4N. (2*2).
Ill let you do the rest of the work to figure out why the 2kg block exerts 4N on the 3kg block.
Quote:  A 2.0 m long, 500 Kg rope pulls a 10 Kg block of ice across a horizontal, frictionless surface. The block accelerates at 2.0 m/s2. How much force pulls forward on:
A) The block of ice
B) The rope 
Again. THe best way to tackle this problems is with force (or free body) diagrams. Again, force due to gravity and normal force apply. but since we arent moving vertically im not gunna bother with them.
(ice)> F(rope on ice))
F(ice on rope) <(Rope)
A) this should be easy. F=ma. F= (10)(2) = 20N
B) Well Newtons third law states that this should also be 20 N. 

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