Railway Science (Physics-Force and Pressure)

The opposing force that opposes the relative motion between two surfaces. It always works in the direction opposite to the direction in which the object is moving or trying to move. The amount of friction depends on the materials from which the two surfaces are made. The rougher the surface, the more friction is produced. When the brake is applied in a bicycle, the brake pad touches the wheel. The friction between the pad and the rim stops the movement of the wheel.

Static friction acts on a body when there is no relative motion between the object and the surface. Sliding friction acts on objects while they are in sliding motion concerning a floor or a surface. Rolling friction occurs when one object rolls on another, like a car's wheels on the ground. Fluid friction is exerted by the fluid on the object that is moving through a fluid.

The upward buoyant force that is exerted on a body immersed in a fluid, whether partially or fully

The force that resists motion when the surface of one object comes in contact with the surface of another. Example - Walking on ground or dry floor, lighting a matchstick. Frictional force is very less on smooth surfaces. Type of frictional force - Static friction, Sliding friction, Rolling friction, Fluid friction.

When an object slides or rolls over another object, force acts between the surfaces of the objects opposite to the direction of motion. Example - Applying brakes to stop a moving vehicle, walking on the road, cleaning the carpet by beating it with a stick. Magnetic Force - The attractive or repulsive force that arises between two electrically charged particles due to their motion. Example - Compass. Electrostatic force - The force between two charged particles at rest. Example: Lightning. Spring force - It is a restoring force as the force exerted by the spring is always in the opposite direction. Examples: Pendulum, rubber band.

Force that resists the sliding or rolling of one solid object over another. Factors Affecting Friction - Nature of the two surfaces that are in contact, the force that is acting on these surfaces. Types - Static friction, Sliding friction, Rolling friction, Fluid friction. Formula: f = µN. where, f (friction force), (µ) coefficient of friction, (N) Normal force.

The object can never stop. Friction reduces the relative motion between two bodies or surfaces in all contact. It always operates in the direction that opposes the direction of the motion. Type of friction - Static friction, Sliding friction, Rolling friction, and Fluid friction. Order of frictional force : Static friction (fₛ) > Sliding friction or Kinetic friction (fₖ) > Rolling friction (fᵣ). Drag (fd) - The frictional force exerted by fluids.

Archimedes' principle (physical law of buoyancy) states that a body when wholly or partially immersed in fluid experiences an upward thrust which is equal to the weight of the fluid displaced by it. Hydrometers, ships, and submarines work on the Archimedes’ principle. Lactometer is used to determine the purity of a sample of milk.

Without treads, the tires would be smooth and would not have enough traction on the road, leading to skidding and accidents. Friction is the resistance to motion of one object moving relative to another. Types of Friction: Static - It acts on objects when they are resting on a surface. Sliding - It is the friction that acts on objects when they are sliding over a surface. Rolling - It is the friction that acts on objects when they are rolling over a surface. Fluid - friction that acts on objects that are moving through a fluid.

Main differences between rolling friction and sliding friction - Rolling friction occurs when an object rolls on a surface while sliding friction occurs when an object slides on a surface or when two surfaces are rubbed against each other. In rolling only a point on the surface remains in contact with the object while in the sliding finite area of the surface remains in contact with the object. So, friction is less in rolling than in sliding.