Jumping off a Bike
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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Update: June 2012