Question:
Examples of Newton's second law?
anonymous
2008-02-07 22:06:27 UTC
what are ways to physically show Newton's second law of motion?
Five answers:
anonymous
2008-02-07 22:31:51 UTC
Well... it depends what you mean by "show".



There really are no ways to "show" Newton's second law of motion. This may come as a surprise to you. Let me explain what I mean by that.



The second law is the DEFINITION of force. It tells you that if you want to measure a force, you have to measure the acceleration of a test mass.



So whenever you "show" the second law at work, e.g. by pulling on a test mass on wheels with a spring force gauge, what you are really doing is to calibrate the device that produces the force (in this case the spring force gauge) against the definition of force. You are not demonstrating the second law... you are simply checking if your force gauge etc. is any good. This would also hold for all other experiments that produce a "known" force and then measure the acceleration of a test mass.



If we wanted to "show" or "prove" the second law of motion, we would need an independent definition of force. There is no such physical definition. Hooke's Law is not a definition of force, it is an empirical law for elastic materials. Neither is any other physical effect that uses matter (e.g. gas in a pressure vessel) an independent force normal.



Sadly, when we teach physics, very often the teacher puts the force gauge on the table right next to the test mass on its little railway cart that allows it to be accelerated without too much friction. The students see this and the student's brain equates



force gauge = definition of force = left hand side



accelerated mass = right hand side



Pull with one Newton (that's what it says right there on the force gauge!), observe an acceleration of 0.1m/s^2 for a 10kg mass.



Pull with two Newton, observe twice the acceleration...



QED Newton's second law.



And that is exactly what Newton's second law is NOT about. It can not be tested and it can not be proven with force gauges.But if you had a spring with unknown spring constant, Newton's second law could be used to measure the spring constant, though...
ultimate reality1
2008-02-07 22:13:45 UTC
It's as simple as picking up an object and letting it fall to the ground.



You can compute the Force of which it hits the ground by observing the mass of it and knowing that the acceleration is actually gravity, which causes things to fall.

F=m*a or in this case F = mass * gravity
?
2016-05-25 14:21:54 UTC
hmmm. You drop a ball of a building, the Force of gravity accelerates the ball to earth.
Da_Gibb
2008-02-07 22:13:12 UTC
well whichever order they go in...



get a couple shopping carts



1) sit in it



2) get two carts and a person in each one. one push the other hard as possible



3) have someone push you as hard as they can 20 or so feet from a wall
anonymous
2008-02-07 22:12:28 UTC
Stepping on the gas pedal will lead to an increase in the car's velocity.


This content was originally posted on Y! Answers, a Q&A website that shut down in 2021.
Loading...