There will be static friction acting at the lowest point. Friction acts to prevent slipping between surfaces--which is exactly what it's doing here. Without friction providing a torque about the center of mass, how could the sphere continue to roll without slipping as it accelerates down the slope?cupid.callin said:
Doc Al said:
Rotational friction is a type of friction that occurs when a rolling object, such as a sphere, is in motion. It is caused by the resistance between the object and the surface it is rolling on, and it acts against the direction of motion, slowing down the object's rotation.
Rolling friction is different from sliding friction in that it only occurs when an object is in motion, while sliding friction can occur when an object is stationary or in motion. Rolling friction also involves the rotation of an object, while sliding friction involves the sliding or dragging of an object along a surface.
The amount of rotational friction on a rolling sphere can be affected by several factors, including the weight of the object, the surface it is rolling on, the shape and size of the object, and the speed of the rolling motion. In general, heavier objects and rougher surfaces will have more rotational friction.
Rotational friction can slow down the motion of a rolling sphere by converting some of its kinetic energy into heat energy. As the sphere rolls, frictional forces act against its motion, causing it to gradually lose speed and eventually come to a stop.
While rotational friction cannot be completely eliminated, it can be reduced by using smoother surfaces, lubricants, or by increasing the size of the rolling object. In some cases, it can also be beneficial, such as in the case of wheels on a vehicle, where friction allows for better control and steering.
