Physics Chapter: Friction Force

Study Notes

Definition: Friction is the force that opposes motion between two surfaces that are in contact
Types of friction:
- Static friction: occurs when an object is stationary and resisting forces that try to make it move
- Kinetic friction: occurs when an object is moving and resisting forces that try to slow it down
- Rolling friction: occurs when an object is rolling on a surface
- Fluid friction: occurs when an object is moving through a fluid (such as air or water)
Factors affecting friction:
- Surface area: increased surface area increases friction
- Normal force: increased normal force increases friction
- Surface roughness: increased surface roughness increases friction
- Velocity: friction decreases as velocity increases

Definition: Gravity is the force that attracts two objects with mass towards each other
Characteristics:
- Gravity is a universal force that affects all objects with mass
- Gravity is a weak force compared to other fundamental forces
- Gravity is always attractive, never repulsive
- Gravity is proportional to the product of the masses of the objects and inversely proportional to the square of the distance between them
Formula: F = G * (m1 * m2) / r^2, where F is the force of gravity, G is the gravitational constant, m1 and m2 are the masses of the objects, and r is the distance between them

Definition: Torque is the rotational force that causes an object to rotate or twist
Formula: τ = r * F, where τ is the torque, r is the distance from the axis of rotation to the point where the force is applied, and F is the force
Units: Nm (newton-meters)
Characteristics:
- Torque is a vector quantity, and its direction depends on the direction of the force and the axis of rotation
- Torque is proportional to the distance from the axis of rotation and the force applied
- Torque can cause an object to rotate, slow down, or speed up

Friction is the force that opposes motion between two surfaces that are in contact.
There are four types of friction: static friction, kinetic friction, rolling friction, and fluid friction.
Surface area, normal force, surface roughness, and velocity affect friction, with increased surface area, normal force, and surface roughness increasing friction, and increased velocity decreasing friction.

Gravity is the force that attracts two objects with mass towards each other.
Gravity is a universal force that affects all objects with mass, and it is always attractive, never repulsive.
Gravity is proportional to the product of the masses of the objects and inversely proportional to the square of the distance between them.
The formula for gravity is F = G * (m1 * m2) / r^2, where F is the force of gravity, G is the gravitational constant, m1 and m2 are the masses of the objects, and r is the distance between them.

Torque is the rotational force that causes an object to rotate or twist.
The formula for torque is τ = r * F, where τ is the torque, r is the distance from the axis of rotation to the point where the force is applied, and F is the force.
Torque is a vector quantity that is proportional to the distance from the axis of rotation and the force applied, and it can cause an object to rotate, slow down, or speed up.
The unit of torque is Nm (newton-meters).

Mass is a measure of the amount of matter in an object or substance, and it is a fundamental property of an object.
Mass does not change, regardless of the object's location or environment.

The SI unit of mass is the kilogram (kg), which is the base unit.
Other common units of mass include:
- Grams (g), which is one-thousandth of a kilogram.
- Milligrams (mg), which is one-thousandth of a gram.
- Micrograms (μg), which is one-millionth of a gram.

Mass is typically measured using a balance or scale, which compares the object's mass to a known standard.
The measurement of mass is often used to calculate other physical quantities, such as:
- Density, which is the mass of an object per unit volume.
- Weight, which is the force exerted on an object by gravity.

Mass is a measure of the amount of matter in an object, whereas weight is the force exerted on an object by gravity.
Mass remains constant, while weight varies depending on the gravitational field the object is in.
For example, an object's mass is the same on Earth and on the Moon, but its weight is different because the gravitational field is different.