Static friction is the friction acting on a body when a body is in a state of rest. In other words, static friction opposes motion in an object at rest. It is a self-adjusting force that adjusts itself to match the applied force. A certain minimum amount of force (limiting friction) is required to overcome static friction. Static friction is a very common type of friction, and we can see examples all around us. In this article, we look at the 25 most common examples of static friction.
Examples of static friction
- Stone on the ground
- A car parked on a slope
- Holding onto objects
- Pushing a heavy object like a truck
- Sticky note
- Legs of a gecko lizard
- Spectacles on our nose
- Making a knot
- An object moving in a conveyor belt
- When we are in a travelator
- Dust sticking onto surfaces
- Water droplets on a windowpane
- Nail in a wall
- Cap of a pen fitting onto a pen
- A shirt hanging on a hanger
- Belt onto our hips
- Hats/caps in our head
- Ring in our hands
- Wearing a watch
- Tiles on a roof
Stone on the ground: A stone resting on the ground will not move unless acted upon by some force. Even the slightest wind cannot push it. It is due to the static friction with the ground. Even if the stone is on a slope the static friction will keep the stone at rest. Static friction is dependant on the mass of the object. So heavier the stone, the tougher it will be to move it.
Pushing a heavy object like a truck: We can push small objects like books, small stones, pencils, etc because these have low static friction. But pushing a heavy object like a cupboard, airplane or truck requires a lot of force. This also depends on the surfaces that we are pushing across. We can even think of pushing a vehicle on a road, but across a sandy dune, it is very difficult.
An object moving in a conveyor belt: When objects are moving in a conveyor belt, they don’t fall down immediately. They are held by static friction. But yes if the speed is very high and forces exceed the limiting friction, then the objects fall down. But generally, the speeds are controlled.
When we are in a travelator: This example of static friction will be very clear. When we are moving to a travelator, there is no relative motion between us and the belt. So in effect, we are in a state of rest. But, actually, we should fall down due to the speed, but the static friction saves us from falling down.
Dust sticking onto surfaces: Dust particles are sometimes very difficult to remove. We even require a vacuum cleaner to suck out the particles. It is due to the static friction that the dust particles remain stubborn. Applying a cleaning fluid will cause fluid friction to reduce limiting friction and make it easier for us to clean.
Nail in a wall: A nail is able to hold onto a wall or a wooden plank due to the friction between the wall and the nail. The value of limiting friction is very high. That is why, when trying to remove a nail, we have to struggle. The static friction will adjust itself to match the applied force until it exceeds the limiting friction.
A car parked on a slope: Common sense tells us that gravitational force on Earth pulls anything that goes up. But an object parked on a slope does not generally slide down the hill. The static friction of the vehicle with the ground holds the vehicle at rest. The brakes on the vehicle also help to increase this friction by arresting the motion of the wheels. You might have noticed that sometimes a brick is placed behind the wheels if the brakes are functioning properly.
Holding onto objects: Without friction, it is impossible to grip onto objects. We cannot hold our cellphones, bottles, etc. When we lift an object, the static friction between our hands and the object help to keep the object at rest with respect to our hands. In this example of static friction, though there is a motion, there is no relative motion.
Sticky note: A sticky note can be stuck to surfaces against the forces of nature like gravity, wind force, etc. The limiting friction is value if very high for it to be disturbed. Here, the cause of friction is chemical adhesive forces.
Legs of a gecko lizard: A gecko lizard is able to stand vertically on wall surfaces due to friction. The static friction allows it to remain in a state of rest even vertically. The friction is caused due to van der Waal’s forces of attraction.
Tying a knot: A knot is held tight into its position. And it is very difficult to untie a tight knot. This is due to the static friction, that tries to keep the rope in its place.
Spectacles on our nose: The spectacles are held by force of friction between the material and our nose and ears. If there was no friction, it would have slipped continuously. Since the type of friction involved here is dry sliding friction, the spectacles are able to stay for a long time on our noses.
Cap of a pen fitted to the pen: A perfectly matched cap sits on top of a cap due to static friction. The shape has to be perfect to get more static friction.
A shirt hanging on a hanger: A shirt placed correctly on a hanger will not fall down. The friction between the shirt and hanger will hold it. The material is also important, the wooden hangers will have more friction compared to plastic ones.
Belt: The belt due to static friction is able to hold our pants onto our hips.
Hats/caps in our head: Our caps/hats are held in our heads without any assistance. The static friction will hold it in its place. The shape of the cap will also determine the value of friction.
Ring in our hands: You might have noticed that a large ring won’t fit into our hands, it will fall off. The ring is able to fit in our fingers and stay there due to static friction.
Wearing a watch: A watch is also similar to a ring and requires static friction to remind in our hands.
Water droplets on a windowpane: You might have observed water droplets on a windowpane on a rainy day. Some heavy droplets will drain away but some ultrafine droplets remain on the pane due to static friction.
Tiles on a roof: Tiles are placed vertically or at a slant. But they are held together by the strong forces of the cement. This can also be considered as an example of static friction. The cause of friction here is chemical adhesion.
What are the most common examples of static friction that we encounter every day?
Most common examples of static friction would include holding onto objects like cellphones, glasses, etc. Wearing clothes, watches, rings, and hats. Sticky notes and other adhesive-based objects.
