3 added 948 characters in body edited Apr 10 '15 at 6:32 user76716 The wheel is moving all the time, but each point on its circumference accelerates and decelerates all the time and when it is in contact with the ground it stops. You can have a clear and convincing explanation watching this animation showing how each point on the wheel describes a cycloid update But remember that the ever-changing acceleration of each point is just an illusion created in the frame of reference of the road, which is at rest. This is due to the fact that the value $$k$$ of the translational forward-velocity of the wheel $$k$$ coincides with the circumference of the wheel $$k = 2\pi r\rightarrow v_w = 2\pi r$$ m/s: If you can, just imagine the car moving at the same speed and the wheel spinning at the same angular velocity but not touching the ground. Or imagine the wheel of a landing plane: as soon as it touches the ground the wheel synchronizes itself to $$v= 2\pi r$$ m/s. -- An illusion of a completely different kind can be experienced by stroboscopic (or wagon-wheel) effect** The wheel is moving all the time, but each point on its circumference accelerates and decelerates all the time and when it is in contact with the ground it stops. You can have a clear and convincing explanation watching this animation showing how each point on the wheel describes a cycloid The wheel is moving all the time, but each point on its circumference accelerates and decelerates all the time and when it is in contact with the ground it stops. You can have a clear and convincing explanation watching this animation showing how each point on the wheel describes a cycloid update But remember that the ever-changing acceleration of each point is just an illusion created in the frame of reference of the road, which is at rest. This is due to the fact that the value $$k$$ of the translational forward-velocity of the wheel $$k$$ coincides with the circumference of the wheel $$k = 2\pi r\rightarrow v_w = 2\pi r$$ m/s: If you can, just imagine the car moving at the same speed and the wheel spinning at the same angular velocity but not touching the ground. Or imagine the wheel of a landing plane: as soon as it touches the ground the wheel synchronizes itself to $$v= 2\pi r$$ m/s. -- An illusion of a completely different kind can be experienced by stroboscopic (or wagon-wheel) effect** 2 added 85 characters in body edited Apr 6 '15 at 13:26 user76716 The wheel is moving all the time, but each point on its circumference accelerates and decelerates all the time and when it is in contact with the ground it stops. You can have a clear and convincing explanation watching this animation showing how each point on the wheel describes a cycloid The wheel is moving all the time, but each point on its circumference accelerates and decelerates all the time and when it is in contact with the ground it stops. You can have a clear and convincing explanation watching this animation showing how each point on the wheel describes a cycloid The wheel is moving all the time, but each point on its circumference accelerates and decelerates all the time and when it is in contact with the ground it stops. You can have a clear and convincing explanation watching this animation showing how each point on the wheel describes a cycloid 1 answered Apr 6 '15 at 5:42 user76716 The wheel is moving all the time, but each point on its circumference accelerates and decelerates all the time and when it is in contact with the ground it stops. You can have a clear and convincing explanation watching this animation showing how each point on the wheel describes a cycloid