Does Newtons 3rd law mean that half of the energy is wasted?

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This may sound dumb to some folks, but lets say I fire a gun. 1000N of force goes into the bullet, and another 1000N of force goes into my body. Even if i strap the gun to the ground, it will just apply 1000N of force to move the earth by a tiny amount. Because of this, does it mean that it isn’t possible to have 2000N of force going to the bullet with the same parameters as before?

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Anonymous 0 Comments

No. You seem to be thinking about momentum rather than kinetic energy.

When you do that, the change in *momentum* of the bullet will be equal and opposite of that of the Earth, but the bullet will have nearly all of the kinetic energy.

Momentum is (mass)*(velocity)

Kinetic energy is (1/2)*(mass)*(velocity)^2

Because of the squared velocity term in the kinetic energy, if two objects have the same momentum, the smaller and faster one will have more kinetic energy than the slow heavy one.

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