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.Continue Reading
In the case of rolling friction, tiny indentations interfere with one another as surfaces roll over one another. Friction makes the wheel catch its grip on the surface and stop slipping, as is the case when a car sits and spins its tires. Once the wheel catches on the road, the car can move forward.
The friction that works to slow down a wheel decreases the wheel's angular velocity, which happens at any angle of surface, but the force of gravity more than compensates for the friction if the angle is downward.
In the case of sliding friction, the force of gravity forces the surfaces together, and a drag force appears between the surface running parallel to them both. The static friction coefficient varies with the surfaces' combined roughness. When the object begins to move, the greater surface area makes sliding friction significantly larger than rolling friction.Learn more about Motion & Mechanics