# When you ride a bicycle, in what direction is the angular velocity of the wheels?

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When you ride a bicycle, in what direction is the angular velocity of the wheels?

c) forwards

d) backwards

i thought it was C (forwards) but the answer is A (to your left).

but why?

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As an object rotates, each particle has a different velocity:

the ‘Speed’ component varies with radius

the ‘Direction’ component varies with angle.

All of the velocity vectors are aligned in the same plane.

It would be confusing and ambiguous to try to choose one particular direction in that plane, but we can be completely unambiguous by choosing a single vector normal to that plane (a vector normal to the plane is normal to ALL of the possible velocity vectors of the rotating object).

The convention used is often called the “Right-hand rule”. The angular velocity vector points along the wheel’s axle. Imagine wrapping your right hand around the axle so that your fingers point in the direction of rotation, with your thumb sticking out. Notice that your thumb points to the left.

So:

By the right-hand rule convention, a wheel rotating on a forward-moving bicycle has an angular velocity vector pointing to the rider’s left.

• John

Angular Velocity Direction

• Liz B

It’s 3:00 in the morning. Are you serious?

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