There are three types of friction. ______________ friction occurs when an object is not moving. ______________ friction occurs when an object is moving against another surface. ______________ friction occurs in the case of wheels or other round objects. The amount of friction depends on two things.First, how ______________ the surfaces are; and second, how ______________ the object is. It is ______________ to keep an object moving than to start it moving. This is because static friction is ______________ than sliding friction.
