0
$\begingroup$

There is a question, Contradiction between law of conservation of energy and law of conservation of momentum? The answers say that earth does gain some velocity that is negligible. So I ask, what if we all push a wall in the same direction? And if we have been pushing walls since so many years, has the velocity of earth increased?

$\endgroup$
1
  • $\begingroup$ momentum is conserved by your feet pushing in the opposite direction and the radiation leaving in heat waves by all of you pushing the wall as hard as you can. $\endgroup$
    – anna v
    Oct 2, 2017 at 11:22

1 Answer 1

1
$\begingroup$

As hinted at in the comment to your question, one must ask: What are you pushing against? That is, whatever force your hands apply to the wall, your feet must apply to the floor in the opposite direction. The end result is that your efforts have no effect. (Well, if you push hard enough, you can knock the wall down, or perhaps just slide across the floor, depending on the coefficient of friction, but you won't cause any net motion of the Earth.)

$\endgroup$
4
  • $\begingroup$ What if we all run togethor in the same direction? Our feets will push back the earth? And so the answer of that contradiction is given wrong by everyone? $\endgroup$ Oct 2, 2017 at 13:40
  • 1
    $\begingroup$ @RamKeswani running on earth is a very complex problem, due to the atmosphere. On an airless world, running would affect the rotation of the planet only until the people stop running. $\endgroup$
    – Asher
    Oct 2, 2017 at 15:45
  • $\begingroup$ @Asher So when someone pushes against a wall, does the feet equalize as said here or the earths speed increases as said by others? Thank you $\endgroup$ Oct 3, 2017 at 15:00
  • 1
    $\begingroup$ If you're pushing against a wall, both you and the wall are "attached" to the Earth, so there's no net change in motion. The wall pushes one way on Earth and you push the other way and those forces are equal. $\endgroup$
    – Asher
    Oct 3, 2017 at 15:24

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.