What is Friction?

Have you seen someone slip and fall off a chair? Did it make you laugh? Imagine if we were constantly slipping of chairs and beds and stairs… life wouldn’t be very fun, would it?

Thanks to friction, this does not happen. Everything would just keep slipping and falling all over the place if it wasn’t for friction.

How does friction affect motion of an object?

Friction is a force that is created when two surfaces move or try to move across each other. The amount of friction produced during this process depends on the texture of both the surfaces and the amount of contact force pushing the two surfaces together.

Friction always opposes the motion or attempted motion of one surface across another surface. As the two surfaces slide against each other, their contact is anything but smooth. They both grind and drag against each other, producing friction. You will find friction everywhere that objects come into contact with each other.

The force acts in the opposite direction to the way an object wants to slide. When you want to stop your bicycle, you press the brake and your bicycle slows down because of the friction between the brakes and the wheels. If you are running on a playground and hear your friend call you and suddenly want to stop, you can because of the friction between your shoes and the ground.

Friction in solids, liquids and gasses

Friction only happens with solid objects, but you do get resistance to motion in both liquids and gases.(States of Matter)

Different solid objects experience different amounts of friction. An eraser on a glass top table will experience more friction than a coin, which will experience more friction, than an ice cube on the same table.

Why do you think you find it difficult to walk in the house after the floor has just been mopped? Your mother cautions you, saying “Don’t walk around now. The floor is wet, you might slip and fall.” This is because liquid creates a barrier between the ground and your shoes and makes the friction much less.

Less friction means it is harder to stop. It is because of this reason that you hear of many accidents during monsoons. Even though the friction of the brakes is still there, the brakes may be wet, and the wheels are not in as much contact with the ground because of the water. Although liquids offer resistance to objects moving through them, they also smooth surfaces and reduce friction.

With gasses and friction it’s a colliding situation, not a sliding one. If the gas is air it is referred to as air resistance. The friction in liquids and gases is due to the property called “viscosity.” A gas, or more particularly a liquid, is described as “viscous” when it resists flow, either of itself or of an object through it. Water is more viscous than air, while honey or treacle is more viscous than water.

Slide a coin across a marble floor and then slide the same coin across a concrete pavement. What difference do you notice? Why does this happen?

For more such interesting physics videos and articles visit our Physics for Kids category.