Understanding Motion, Force, and Energy in Physics
Item 5
Force is an interaction between two objects. There are four types of forces:
- The gravitational force
- The electromagnetic force, which causes chemical reactions
- Strong nuclear forces, which are responsible for the stability of atomic nuclei
- Weak nuclear forces, which are responsible for the instability of atomic nuclei
Weight (P) = Mass (M) * Gravity (G)
Item 6
Movement is a physical phenomenon defined as any change of position in space experienced by bodies in a system with respect to themselves or another body, which is taken as a reference. A body in motion describes a path.
Path
It is the locus of successive positions through which a body in motion passes. The trajectory depends on the reference system describing the movement, that is, the viewpoint of the observer.
Displacement
The length of the path is described by a length and corresponds to the distance between the initial and final points of its trajectory. It is represented by the length of the straight line joining the starting point to the endpoint.
Direction
This is the angle formed by the trajectory with an imaginary axis, which is generally horizontal.
Speed
Speed is a physical quantity expressing the vector character of the movement of an object per unit of time. In everyday language, we use the words “speed” and “velocity” interchangeably. In physics, we distinguish between them. Quite simply, the difference is that speed is a rate in one direction. When we say that a car is traveling at 60 km/hour, we are indicating its speed. If we say that a car is moving at 60 km/h north, we are specifying its velocity. Speed describes how fast an object moves; velocity tells us how fast it moves and in what direction.
Velocity = Displacement / Time
Speed
Speed, also called “rate of motion”, is the relationship between distance traveled and time spent in travel. A car, for example, runs a number of kilometers per hour, which can be 110 km/h. Speed is a measure of how fast an object moves. It is the rate of change of distance traveled, as the expression “rate of change” indicates that we are dividing a number by time. Therefore, speed is always measured in terms of a unit of distance divided by a unit of time.
Speed = Distance Traveled / Time
Acceleration
In physics, the term “acceleration” is a vector quantity that applies to both increases and decreases in speed in a unit of time. For example, the brakes of a car can produce large retarding accelerations, that is, they can produce a large decrease in speed per second. This is sometimes called deceleration or negative acceleration. The term “acceleration” applies to changes in direction as well as to changes in speed. If you travel a curve with a constant speed of 50 km/h, you feel the effects of acceleration and a tendency to lean towards the outside of the curve (inertia). You can go through the curve with constant speed, but your velocity is not constant because your direction changes at every moment. Therefore, your state of motion changes, that is, you are accelerating.
Acceleration = Speed / Time
Sense
This determines whether the body has moved to the right, left, up, down, or even in other directions. It also determines the direction in which the body is moving.
Energy
In physics, energy is defined as the ability to perform work. It is manifested in physical systems, for example, by raising an object, transporting it (movement), deforming it, or heating it. Energy is not a real physical state nor an “intangible substance”, but a scalar quantity that is assigned to the state of the physical system. That is, energy is a tool or mathematical abstraction of a property of physical systems. For example, one can say that a system with zero kinetic energy is at rest.
Energy is measured with the unit “joule (J)”.
Force
In physics, force is a physical quantity that measures the intensity of the exchange of momentum between two particles or particle systems (in the language of particle physics, we speak of interaction). According to a classical definition, force is any agent capable of modifying the amount of movement or shape of material bodies.
In the International System of Units, force is measured in “Newtons (N)”.