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I was wondering why is it when you jump off a speeding bike, it is hard to stand on your feet without tumbling over? Can you explain?

Conservation of momentum. While you ride a speeding bike, the mass of your body has a certain velocity, and hence momentum. Momentum = mass x velocity Momentum is conserved, meaning it takes an outside force to change it. When you jump off, you still have the momentum, but to stand up on your feet, you need to stop, reducing your velocity and momentum to zero. To do this you must apply force. The only way you can apply the force needed to stop you is with your feet. When your feet stop and the rest of you wants to keep going, you have a torque, which tends to rotate your body (face first into the ground.

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