Friction is the force that makes it difficult to slide one object over another. Imagine trying to slide a heavy box across the floor, friction is what makes it hard to move. Friction is also what helps us walk, by providing grip between our shoes and the ground.
Fs ∝ R
The ratio between limiting force and normal reaction R is constant that is represented by
coefficient of friction
Fs = μR
When a body is placed on a surface its weight w acts downward then according to Newton’s third law of motion
R = W
Fs = μmg
The force that acts on a stationary object and opposes its ability to start moving is known as static friction. The maximum value of static friction is referred to as “limiting friction.”
Example: A heavy box sits on a flat surface, with a person pushing on it with a certain force. Despite the force being applied, the box remains still. This is because the force of static friction, acting in the opposite direction of the applied force, is equal in magnitude and prevents the box from moving. As the person increases the force applied, the force of static friction also increases, until it reaches its maximum value, known as the limiting friction. At this point, the box is on the verge of moving, but still remains at rest due to the equal and opposite force of static friction. Only if the person applies a force greater than the limiting friction, will the box begin to move.
“The force that opposes the motion of a moving object is known as friction. It is noteworthy that, in nearly all circumstances, the force of static friction exceeds that of kinetic friction.”
Example: Consider a heavy box resting on a flat surface, with a person trying to push it. Initially, the box does not move as the force of static friction between the box and the surface is greater than the force applied by the person. However, once the applied force exceeds the maximum static friction, the box starts moving and kinetic friction comes into play. The force of kinetic friction is less than the force of static friction and opposes the motion of the box. As a result, it takes less force to keep the box moving once it’s already in motion than to get it moving from a static position due to the lower force of kinetic friction.
When one body slides over another body, the friction between the two surfaces is referred to as sliding friction.
Example: As a car drives down a road, the tires slide over the surface of the pavement. This sliding motion creates friction between the tires and the road, which helps the car to slow down or stop when the brakes are applied. However, if the road is wet or icy, the sliding friction between the tires and the road can decrease, making it more difficult for the car to stop quickly. In this case, the driver must take extra caution to avoid accidents.
When a body moves on wheels, the friction is called rolling friction, which is much less than sliding friction.
Example: A cyclist is riding a bike on a smooth road. The wheels of the bike are rolling on the surface of the road, and the contact between them causes rolling friction. This type of friction is much less than sliding friction, which would occur if the bike was dragged or pushed along the road. The rolling friction allows the cyclist to move forward with less effort and also prevents the wheels from wearing out too quickly.
In summary, friction plays an important role in many everyday activities and industrial processes.
Hazardous Work Environment: Friction can create hazardous work environments, such as in mining and construction, where workers may be exposed to heat and sparks generated by friction.
Overall, friction can be both helpful and harmful, and it’s important to understand its effects to make the most of its benefits and minimise its drawbacks.
There are several ways to reduce friction:
Note: These are the general ways to reduce friction, the actual methods may vary based on the specific scenario and application.