Physics Fundamentals: Motion, Forces, and Electromagnetism
Kinetic
Reference Frame
An oriented straight line in which motion occurs. It presents an origin and an axis.
Position
The distance between the object and the origin of the reference frame.
Displacement
Difference between any two positions. It moves when it changes position regarding the reference frame.
Velocity
Difference between any two positions: incremento de e: incremento de t.
Acceleration
The measurement of the rate at which the velocity of a body varies: incremento de velocidad entre incremento de tiempo.
Types of Motion
Uniformly Accelerated Motion
There is a constant positive acceleration.
Uniform Motion
The velocity is maintained, so its acceleration is zero.
Forces
Any interaction between two bodies by contact or at a distance that causes deformation or a change in their state of resting or motion. Act at a distance or at contact by deformations or changes in the body’s state of motion. A body deforms as a result of forces. When its length varies along the force’s line of action according to the behavior of the body, it could be:
- Rigid: Don’t deform.
- Elastic: After deforming, they regain their initial length.
- Plastic: After deforming, they don’t regain their initial shape.
Vectors are arrowhead segments showing the factors of a force. They show:
- Direction: An imaginary line on which the force acts.
- Magnitude: Value of the force that is represented by the length of the arrow.
- Point of application of the force.
- Sense: There are two senses in one direction.
Hooke’s Law
That the force applied to an elastic body is directly proportional to the deformation caused. The ratio between the force applied and the elongation is constant and it is called the spring constant (k). k = force : constant of length.
Acceleration
A force is applied to an object, changing its state of motion. FUERZA = MASA . ACELERACIÓN.
Friction
Fluid Friction
It happens when a body moves in a fluid like water or air. It is due to the opposition of the fluid particles to separating. Reduce by changing the shape of the body.
Solid Friction
It happens when two solid bodies come into contact. It is due to the irregularities of the bodies that come into contact. Reduce by adding a liquid between the two bodies.
Gravity
A force that acts at a distance between two bodies that have mass. It increases with the value of these masses and decreases with the distance that separates these bodies.
Characteristics
- Decreases with distance.
- There is no need to contact between the bodies.
- Increases with the mass of the bodies.
- It always goes towards the center of the bodies.
Weight
Is the force with which a planet attracts us. W = MASA * GRAVITY.
Light Time
The speed at which light travels at a time. 300,000 km/s.
Electric Force
The force that appears between two bodies when they are charged.
Characteristics
- No need for contact.
- Repulsive between charges of the same sign.
- Increases with the value of charges.
- Decreases with distance.
Static Electricity
An imbalance of electric charges within or on the surface of a material.
Electric Current
A flow of electrons.
Gravity Force vs. Electric Force
Similarities
- Acting at a distance.
- The value decreases with distance.
Differences
- Gravitational force always attractive.
- Gravitational attractive or repulsive, and the masses are always positive, but the electric charges can be positive or negative.
Acquire Electric Charge
By Rubbing
When two bodies in contact slide together, the charges of one go to the other.
By Contact
When a charged body touches a neutral body, it gives the neutral body part of its charge.
By Induction
When a charged body comes near a neutral body, it induces the separation of charges.
Magnetic Force
Characteristics
- Decreases when the distance increases.
- It can be attractive or repulsive.
- Magnets have two parts: North poles and South Poles.
- It only affects certain materials like iron.
Electric Force vs. Magnetic Force
Similarities
- They act at a distance.
- There are two types of charges.
Differences
- Electric forces appear only in a body with one charge.
- The charges can move through matter in electric, in magnetic, we cannot separate the poles, and the poles cannot move through matter.
Uses of Electromagnetism
To obtain, transport, and use energy.
To Obtain Energy Through a Magnetic Field
A conductive coil is rotated through a magnetic field, the changing magnetic field inside the loop introduces a current through the loop.
Magnetism Through Electricity
An electric current creates an area of influence around itself called a magnetic field, and it behaves like a magnet.