why is sliding friction less than static friction and why is rolling friction is less than sliding friction
Answers
When an object slides across the ground, it has much more surface area in direct contact with the ground, which means that the amount of friction is significantly higher. When an object rolls along the ground, only a minuscule point on the object contacts the ground at any point in time, making the stopping force much weaker.
Static friction is greater than kinetic friction because of irregularities between the static object and the surface upon which it rests. The irregularities mesh together making it more difficult to start movement than to keep the object in motion.
Static friction is the friction that keeps an object in place. This friction must be overcome by energy to move the object. Because of a combination of surface irregularities and electrical charges between the object and the surface, the energy required to initially move the static object is greater than the energy required to keep it in motion. Because it takes more energy to move the static object, physicists say that static friction is greater than kinetic friction. The smoother the object and the smoother the surface the smaller the difference between the amount of static friction and the amount of kinetic friction.
Why is static friction more than sliding or rolling friction?
Ans. Static friction acts on a body at rest, irregularities on the surfaces in contact get
interlocked, so maximum force is required to overcome this friction.
In sliding friction, the object is sliding over another surface, the motion prevents the
interlocking of the surface in contact, so friction is lesser than in static friction.
In rolling friction , wheels or rollers are the points of contact between any two surfaces
and when wheels roll over the surface, frictional force is least .
Hope it helps :)