0

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?

Qmechanic
  • 201,751
Ram Keswani
  • 2,151
  • 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. – anna v Oct 02 '17 at 11:22

1 Answers1

1

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.)

Ben Niehoff
  • 1,051
  • 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? – Ram Keswani Oct 02 '17 at 13:40
  • 1
    @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. – Asher Oct 02 '17 at 15:45
  • @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 – Ram Keswani Oct 03 '17 at 15:00
  • 1
    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. – Asher Oct 03 '17 at 15:24