Static Friction: The Force That Holds Objects in Place
by Yuvi K - December 19, 2023
What Is Static Friction?
Static friction is a force that prevents an object from moving when pushed or pulled. It is the opposing force that balances an unbalanced force and prevents an object from slipping or sliding. It is also known as friction force and can be found in everyday objects like cars, bicycles, and skateboards.
In physics, static friction is a type of force that is directed away from the direction of motion. It is the result of two surfaces, such as a car tire and a road, that oppose each other and act to prevent the movement of an object. This type of friction force is the cause of objects staying still or “static.”
Static friction is a force that must first be overcome before an object can move. It is not a constant force, and it varies depending on the surfaces involved and the force that is applied to the object. This friction force acts under static conditions, meaning it is always present when two surfaces interact with each other.
How Does Static Friction Work?
The magnitude of static friction is proportional to the normal force, or the perpendicular force acting between two surfaces, such as a block on a surface or a tire on the road. When two objects are touching, the normal force due to their gravitational attraction increases and, in turn, the static friction force increases. This force acts in the opposite direction of the applied force and increases as the applied force increases.
The magnitude of static friction can also depend on the coefficient of static friction (μs), which is the ratio between static friction force and the normal force acting between two surfaces. The coefficient of static friction is a measure of the stickiness of the surfaces.
The Maximum and Minimum Value of Static Friction
The maximum value of static friction, known as the limiting (sādak) static friction or the friction limit (sādak se judi limit) (FS max), is calculated using the formula:
FS max = μs × FN
where μs is the coefficient of static friction and FN is the normal force acting between two surfaces.
The minimum value of static friction is a non-zero but negligible amount of force known as the minimum static friction (mukhya sādak se judi) (FSmin). This force acts in the opposite direction of the applied force and is usually very small.
Examples of Static Friction
Static friction is found in many everyday objects and situations, such as:
- Pushing a car to start it (The car tires must overcome static friction before they can start moving)
- Opening a drawer
- Pulling a door open
- Typing on a keyboard
- Tying a shoe
- Walking on a flat surface
Static friction can also be found in many scientific and industrial processes. For example, static friction is used in braking systems in cars and other vehicles, in components of pressuredialysis machines, and in piston engines.
How to Reduce Static Friction?
The amount of static friction can be reduced by applying a lubricant, such as water, oil, or grease, between two surfaces. Lubricants reduce the surface area of contact between two objects, which reduces the normal force and, therefore, the static friction. Other methods of reducing static friction include applying a small external force parallel to the direction of motion and increasing the static coefficient of friction by making the surfaces rougher or adding tessellations.
Conclusion
Static friction is an important force that prevents objects from slipping or sliding on each other. This force is found in many everyday objects and situations and plays an important role in safety and efficiency in some industrial and scientific processes. The magnitude of static friction can be controlled by reducing the surface area of contact between two surfaces and by applying external forces or by adding lubricants.
As static friction is an opposing force, it must be overcome before an object can move. Static friction is the first force that must be overcome in order to initiate motion, and understanding and controlling it can be beneficial in many applications.
