Brain Teasers
Two Bullets
A piece of firewood is standing on end. Which is more likely to knock the piece of wood over - a lead bullet fired from a gun or a rubber bullet of the same mass travelling at the same speed (and hitting the same spot)?
Assume that the rubber bullet does not disintegrate on impact.
Assume that the rubber bullet does not disintegrate on impact.
Hint
The rubber bullet will ricochet off of the wood - what difference does this make?Answer
The rubber bullet will be more likely to knock the wood over. The lead bullet will embed itself in the wood, so the wood will have to absorb enough energy to stop the bullet's momentum. The rubber bullet will ricochet off of the wood, so the wood will have to absorb enough energy to stop the bullet PLUS send the bullet back in the opposite direction. The rubber bullet will supply more total force to the wood and will therefore be more likely to knock it over.Hide Hint Show Hint Hide Answer Show Answer
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