Question #9b866
1 Answer
Bicyclist must create a centripetal force to keep on the curve. Without it he will continue going straight and, since the wheels are directed towards the curve, the bicycle will turn and he will fall.
Explanation:
In a straight movement there are three forces acting on a bicyclist:
(a) gravitation (straight down),
(b) vertical reaction of a bicycle's seat (straight up) and
(c) pull of the bicycle forward applied through horizontal reaction of a seat and through hands holding the bicycle frame (straight forward).
Forces (a) and (b) nullify each other because they are equal in absolute value and act in opposite directions, so a bicyclist moves forward as a result of force (c).
On a curve a bicyclist turns the front wheel towards a curve. If bicyclist continues to sit vertically, the same force (c) as above moves him at a straight line forward, while forces (a) and (b) would nullify each other. The bicycle, however, is directed along the curve. So, a bicyclist would go straight, bicycle wheels, however, will turn and a bicyclist will fall off.
To stay on a curve the bicyclist must somehow introduce a force moving him towards the curve to stay on the bicycle. The way he does it is by leaning towards the curve. His gravity (a) is still directed vertically down, but the vector of reaction of a bicycle seat (b) now is not vertically up, but tilted to the curve. The sum of these two forces is a horizontal centripetal force needed to turn the bicyclist towards the curve, so he stays on the bicycle.
If the speed is higher on a curve, a bicyclist must change its direction from straight forward to a curved faster, which implies the need for stronger centripetal force. That can be done only by leaning further towards the curve. That's why faster turns require greater tilt of a bicyclist towards a curve to increase the centripetal force.
