Question

friction quiz 4th
(1). list the four types of friction.
(2). if an object has a frictional force applied because it is falling through the air, what type of friction is the object encountering?
(3). give one example of when friction is used and one example of when it is reduced.
(4). define friction.
(5). t/f objects that are sitting still will not encounter friction.

Explanation:

(1) The four types of friction are static, sliding, rolling, and fluid friction. Static friction resists initial motion, sliding friction acts when surfaces slide, rolling friction is for rolling objects, and fluid friction occurs in fluids like air or water.
(2) When an object is falling through the air, it encounters fluid friction (air resistance).
(3) Friction is used when walking (shoes grip the ground). It is reduced by using lubricants like oil in machinery.
(4) Friction is a force that resists the relative motion of two surfaces in contact.
(5) False. Objects at rest can experience static friction if there is an applied force trying to make them move.

Answer:

(1) Static friction, sliding friction, rolling friction, fluid friction
(2) Fluid friction
(3) Used: Walking; Reduced: Using oil in machinery
(4) A force that resists the relative motion of two surfaces in contact
(5) False