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 Subject: Basic Mechanical Physics Category: Science > Physics Asked by: cchanceus-ga List Price: \$5.00 Posted: 19 Sep 2006 17:25 PDT Expires: 19 Oct 2006 17:25 PDT Question ID: 766776
 ```I am disputing these questions with a fellow peer and would like a professional to finalize this debate. 1. A person walking on a level surface moves forward because the forces of? a) his feet pushing on the ground b) the ground pushing on his feet c) either 2. Newton's second law states that if a net force acts on an object, it will move at constant velocity a) True b) False```
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 Subject: Re: Basic Mechanical Physics From: qed100-ga on 19 Sep 2006 22:37 PDT
 ```Here's a summary of Newton's three laws of mechanics. It should help you to clarify the problems. [1]- Inertia. A body's motion is quantified by its momentum (p), which is proportional to both its mass (m), and its velocity (v). In other words, p = mv. Changing velocity = acceleration (a). A body of constant mass in isolation travels with zero acceleration: it neither speeds up nor slows down, nor does it change direction. In other words, its momentum doesn't spontaneously change by itself. It has inertia. [2]- Force. Changing momentum = force, F. Force is quantified as F = ma. [3]- Conservation of momentum. Forces are induced via interactions between pairs of bodies, A & B. An interaction between A & B will leave their total momentum unchanged. In other words, if A alters B's momentum by amount d, then B changes A's momentum by -d. The two amounts add up to zero overall. A & B exert equal sized forces upon each other, but in opposite directions. Whether A & B are attracting or repelling, there will be a unique point between them, their mass-center, which has its own momentum, which is the total momentum of the two bodies A & B.```
 Subject: Re: Basic Mechanical Physics From: cchanceus-ga on 20 Sep 2006 18:00 PDT
 ```I believe the answer to the first question is either and the second question is true. I am being told my answers are incorrect. Thoughts?```
 Subject: Re: Basic Mechanical Physics From: barneca-ga on 20 Sep 2006 20:11 PDT
 ```i wouldn't normally answer what i suspect is an obvious homework question, but i think question 1 is somewhat poorly worded, at least for a beginner. an object accelerates because of forces applied to that object, not because of forces that object applies to other things. your thought that it is "either" shows you know the two forces have equal magnitude, but you have to also understand that they are in opposite directions. which force is in the same direction as the person's motion? qed100 has answered question 2 for you, all you have to do is read (and understand) what they wrote. if you plan on spending \$5 for every homework problem you get stuck on, your parents are NOT going to be happy (or, if you're older and paying your own way, you could have bought a pitcher at happy hour with that). whether you're in high school or college, teachers, professors and teaching assistants have already been paid, by you, to help you with this stuff, all you need to do is go to their office hours and ask for help. -cab```
 Subject: Re: Basic Mechanical Physics From: ashokrr-ga on 22 Sep 2006 09:11 PDT
 ```my naswer to this is that if u are walking on the surface u act some force on whaich has vbeen the positive force where according to netons laws of equal and oppsite and equal reaction he same amount of force is exerted on the foot u hav exerted on the surface here u can bee made to walk furhter which helps u in the direction of the force. if u sudddnely move oppsirte the force of replusion acting on the foot with the accleraion of the body reples u to undisurb and u may fall these are things two got unnoticed in the walk. 2. if a net force acts on the body its to move if u are thing that if the force is acting on the stone its not moving u can see them as a hill is not moving though some force id=s acting on the every body exised in the universe```
 Subject: Re: Basic Mechanical Physics From: harrysnet-ga on 06 Oct 2006 15:51 PDT
 ```1. Answer is (b) the ground pushing on his feet. When you are stationary and start moving is because a force is acting on you. Of course this is generated by the action-reaction law when your feet push the ground, but that is not moving you (in theory it moves the whole earth backwards and very tiny amount backwards). 2. Answer is (b) False. A force causes acceleration, that is a velocity change. So a non zero force will cause continuous acceleration (it doesn't even have to be constant), which means that the velocity changes continuously.```
 Subject: Re: Basic Mechanical Physics From: ukbikerman-ga on 13 Oct 2006 03:48 PDT
 ```Surely the answer is neither. Force needed is horizontal and the only choices are vertical. Without the coefficient of friction then guy is going nowhere,,,```
 Subject: Re: Basic Mechanical Physics From: barneca-ga on 13 Oct 2006 06:58 PDT
 ```"...the only choices are vertical..." it doesn't say that anywhere in the question. -cab```