In the face of ancient grand buildings, we could not help but have a problem: As far back as hundreds of years ago, there was no machinery. What methods did our ancestors use to transport the heavy stones and wood needed to build buildings?
It turns out that the methods used by our ancestors still exist today. When you carry things, put a few round bars on the pad and it will be much lighter when you push them. This is because when the object slides on the ground, there is a sliding frictional resistance where it comes into contact with the ground. When the object rolls on the ground, the resistance is the rolling frictional resistance. There is such a phenomenon in daily life that our trolleys will be lighter if they are loaded with ball bearings. This actually implies a very simple physical principle. In general, the rolling frictional resistance is only one-fortieth to one-sixth of the sliding frictional resistance, so rolling objects are much less laborious than pushing the object to slide.
By the same token, the friction between the wheel bearing
and the journal of a car without a ball bearing is also sliding friction, and the resistance is relatively large. Such a wheel bearing is not only easy to wear, but also the car does not run fast. When the car with the ball bearing is activated, the axle of the wheel rolls on the ball. The balls roll along the raceway around the bearing. In this way, the sliding friction is turned into rolling friction, and the resistance is greatly reduced, so the car becomes light and labor-saving.