Question

A father and son pushed their car to bring it to the side of the road as it had stalled in the middle of the road. They experienced that although they had to push with all their might initially to move the car, the push required to keep the car rolling was smaller, once the car started rolling. Explain.

Answer 1

Frictional force

1. Frictional Force is the force created when two surfaces move against one another.
2. The imperfections on the two surfaces in contact generate friction. As a result, when one object passes over another, the imperfections on the surface become intertwined, causing friction. The rougher the surface, the more imperfections, and friction there will be.

Analyzing the given data

1. When we push something against friction, we must add force in order to simply move the object.
2. When we apply force, static friction occurs. It prevents the thing from moving. When we raise the force, the static friction value increases as well, but after a certain point, the static friction cannot grow anymore. The object is about to move.
3. At this point, the object is about to move; as we apply more force, the object begins to move; friction decreases slightly as motion begins; eventually, it becomes constant, and we can apply a constant force to move the object (i.e., we don't need to keep increasing our force)
4. To overcome static friction, we must apply a larger force to move an object.