Posted October 3, 2005 Ok, I am completely stumped on this Physics question. None of my friends know it so the teacher might have gone over it to quickly or something... anyway, bear in mind I'm only 14 so this question is very simple. What is gravities opposite force? Like why do we stay here, why don't we sink to the ground? Share this post Link to post Share on other sites
Posted October 3, 2005 It's the 'normal' force (freely translated from dutch so terribly wrong). It's 'normaalkracht' in dutch. Please, allow somebody more competent to answer this Share this post Link to post Share on other sites
Posted October 3, 2005 i think it's friction, although i may be wrong. Share this post Link to post Share on other sites
Posted October 3, 2005 I think its because theres an 'upwards' force, and a 'downwards' force and together they keep us stable or something. I dunno, I could be wrong. Share this post Link to post Share on other sites
Posted October 3, 2005 basically the mass of the earth opposes gravity when we are on the ground and as has been said already a normal force generated by the earth opposes gravity Share this post Link to post Share on other sites
Posted October 3, 2005 Isnt it something like the force of floating or weightlessness? Share this post Link to post Share on other sites
Posted October 3, 2005 basically the mass of the earth opposes gravity when we are on the ground so yeah, similar to what I said. If one force is greater than the other then we move, if they are equal then we stay still. Share this post Link to post Share on other sites
Posted October 3, 2005 Ok, thanks for the help guys! Share this post Link to post Share on other sites
Posted October 3, 2005 The technical for the opposition to your weight (the force your mass exerts due to gravity) is "contact force". It follows Newton's third law, which is commonly cited as "every action has an equal and opposite reaction". The ground you stand on exerts an opposite "contact" force equal to your weight, so you don't move. If you are standing on snow, the force is less than your weight so you sink. It isn't tecnichally correct to think of gravity as a force. It's the fact that all objects warp space-time, so objects recieve a weight corresponding to their mass depending on the objects they are nearby (a big simplification). Share this post Link to post Share on other sites
Posted October 3, 2005 I might have got the wrong idea but does he mean Air Resistance (pushes upwards as something is being pulled down by gravity) they are opposite as they work in different directions. Or maybe I'm being lame... meh I had a crap Physics teacher last year... and I never really payed attention so yeah... Share this post Link to post Share on other sites
Posted October 4, 2005 Gravitational force is mutual, F=(G * m1 * m2)/(r^2) where r is the distance the centers of mass the two objects are apart and G is the gravitational constant. Basically you exert the same gravitational force on the earth as the earth does on you. However in gsce probelms (as opposed to planatary motion) then it will be the normal contact force. This acts perpendicularly to the urface the object is resting on and is equal to the perpendicular force due to to gravity on the surface. If you want more help try out http://www.s-cool.co.uk it should help you out. hope that helped. If you need more help just ask, and air resistance is for free fall objects. but there arent many at gcse. It could be a number of things so could you describe the situation the problem is set in? Share this post Link to post Share on other sites
Posted October 4, 2005 "Normal" force, (pusing you up) is essentially the build up of the strong nuclear forces. For example, if you stand on a floor, gravity is pulling you down. The resultant force, is provided by the "resistance" (for a lack of a better word) of the atoms in the floor. Your weight is pushing them together, slightly. This is repelled by the forces that exist between the particles in an atom. Cumatively this balances out gravity. Share this post Link to post Share on other sites
Posted October 4, 2005 It's the 'normal' force (freely translated from dutch so terribly wrong). It's 'normaalkracht' in dutch. Please, allow somebody more competent to answer this You're right! It's called the normal force. It's just the force with which the Earth pushes back on you. If you're just standing around, you're not moving hence all forces are balanced and the normal is the exact opposite of gravity. I did this years ago in high school, but I still use it now as an engineering student in university. Share this post Link to post Share on other sites
Posted October 4, 2005 No it aint....It's contact force like Supergrunch said. I do A2 Physics thank you :p Share this post Link to post Share on other sites
Posted October 4, 2005 its contact force people! Take The quiz yourself! Share this post Link to post Share on other sites
Posted October 4, 2005 its contact force people! Easy to say 20 minutes after the Physics expert comes in :P http://www.cord.edu/dept/physics/p128/lecture99_11.html ==> This basically says what I was thinking, but: http://en.wikipedia.org/wiki/Contact_force also kind of says what I was thinking.... does contact force apply to the earth and normal force to objects ON the earth? I'm confused at the difference in meaning between the two (if there is one) Share this post Link to post Share on other sites
Posted October 4, 2005 The answer is the reaction force, or normall reaction force that the ground provides upwards, to go into more detail you could go onto say about the fact atoms don't collapse into them selfs due to the negative electrons repelling. It has to follow neutons 3rd law , "every reaction has an opposite and equal reaction". Share this post Link to post Share on other sites
Posted October 4, 2005 The answer is the reaction force, or normall reaction force that the ground provides upwards, to go into more detail you could go onto say about the fact atoms don't collapse into them selfs due to the negative electrons repelling. It has to follow neutons 3rd law , "every reaction has an opposite and equal reaction". It doesnt really matter what you call the force, Contact, Reaction or Normal. In this context its all the asme, because Normal is in situe, or always about which it is, and reaction is the ground exerting a reacting force upon you. Contact speaks for itself. Share this post Link to post Share on other sites
Posted October 6, 2005 No it aint....It's contact force like Supergrunch said. I do A2 Physics thank you :p You just call it a different name...maybe that's how you British work? Always trying to be different. I've studied in Canada and the US and every text book calls it the "NORMAL" force. I'm not saying your "contact' force or whatever is wrong, it's just not what everybody else calls it. What is A2 physics anyway? I go to Concordia University and I have no clue what that is...or is it just a different way of calling a certain course? Share this post Link to post Share on other sites
Posted October 6, 2005 It's just different words for the same thing- in England it is called both the contact force and the normal force. Share this post Link to post Share on other sites
Posted October 6, 2005 Thought it was Normal Reaction Force.. I should really listen more in physics. Funny how the easiest questions stump you. Share this post Link to post Share on other sites
Posted October 6, 2005 It doesnt really matter what you call the force, Contact, Reaction or Normal. In this context its all the asme, because Normal is in situe, or always about which it is, and reaction is the ground exerting a reacting force upon you. Contact speaks for itself. Very true, the offical term allways changes with exam boards ect, and can vary from teacher to teacher. Share this post Link to post Share on other sites
Posted October 6, 2005 What is A2 physics anyway? I go to Concordia University and I have no clue what that is...or is it just a different way of calling a certain course? A2 Physics is A-Level Physics. A-Levels are whats studied at college and 6th form in this country, they are probably the same to what you study at high-school between the ages of 16-18, or if you want to be uber pedantic 17-18 for A-Level or A2 and 16-17 for AS Levels. Share this post Link to post Share on other sites
Posted October 6, 2005 Dont confuses him with AS levels! Half of England dont understand them! :P Basically, A2+AS levels = a full Advanced Level (or A Level for short) which is what kids study in education from 16-18, as Offerman said. Share this post Link to post Share on other sites
Posted October 6, 2005 Don't worry BlackFox, I've not been listening and trying to tak in stuff I don't understand.. it's all just random words to me. Share this post Link to post Share on other sites
