Timeline for Is jumping the result of normal force or action-reaction?
Current License: CC BY-SA 3.0
16 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 5, 2015 at 0:23 | vote | accept | Michael Yaworski | ||
| Mar 4, 2015 at 20:10 | comment | added | Michael Yaworski | @BowlOfRed I think the work is done onto you. The normal force acts on you and you are displaced. | |
| Mar 4, 2015 at 19:05 | comment | added | BowlOfRed | $W = F \times d$ If we assume the floor is not moving, then it is doing no work. This is not the case in the elevator example. Most assuredly, it is not accelerating the bottom of your shoe. | |
| Mar 4, 2015 at 18:19 | answer | added | Bill N | timeline score: 1 | |
| Nov 24, 2014 at 22:00 | comment | added | TZDZ | @David Yeah, but that is precisely not the case here. About the difference, since neither the floor slope neither the direction of the jump are stated, we can't say if the reaction force is purely normal. | |
| Nov 24, 2014 at 21:17 | answer | added | Rhino | timeline score: 0 | |
| Nov 24, 2014 at 20:51 | comment | added | DLV | I meant to say that a force that is always normal to an objects velocity does not do work. | |
| Nov 24, 2014 at 16:50 | comment | added | DLV | A normal force is perpendicular to a surface. A force being exerted normal to an object cannot do work, the classical example is the lorentz for e&m. I say a normal force can do work: take for instance yourself on an accelerating elevator.Note: normal means at a 90º angle! | |
| Nov 24, 2014 at 16:39 | comment | added | DLV | I know they are different, however in this case the normal force is the reaction force. I hope I'm not screwing up. | |
| Nov 24, 2014 at 7:24 | comment | added | TZDZ | @mikeyaworski Here are some clues to guide your reflexion : 1. What is the definition of work ? 2. Is the center of mass of a person enough to describe his position ? 3. When you jump, do you feel like the earth is giving you energy ? | |
| Nov 24, 2014 at 6:07 | comment | added | TZDZ | @David I don't know how it's taught in other countries, but the "normal force" here should be the normal component of the reaction force. In general, they are different. | |
| Nov 24, 2014 at 5:34 | comment | added | Michael Yaworski | @David I was taught that the normal force is not the reaction force. That's a misconception. However, you're right that Newton's third law would seem to be violated. I'm not sure. | |
| Nov 24, 2014 at 5:31 | comment | added | C. Towne Springer | It is an interesting question. Work is being done by one part of the body on another. You accelerate the upper part of the body and give it enough momentum to drag along the rest. Pretty complicated. And when you leave contact with the Earth, I wonder if it is as complicated as the rocket equation? You have inspired me to draw some pictures. | |
| Nov 24, 2014 at 5:14 | comment | added | DLV | The reaction force is the normal force. If you think they are different then you'll probably see Newton's third law is being violated. | |
| Nov 24, 2014 at 4:53 | comment | added | mmesser314 | It sounds like a question of semantics. When you jump you exert a force on the ground. The reaction force is the force the ground exerts on you. Both are normal to the ground. The reaction force does work on you. A magnetic field exerts a force on an electron that is normal to the electron's velocity. That can do no work on the electron. | |
| Nov 24, 2014 at 4:32 | history | asked | Michael Yaworski | CC BY-SA 3.0 |