Module 2

• The first to suggest the concept of gravity changing many of popular beliefs of his time.

  Galileo Galilei
• The acceleration due to gravity is relatively constant near the Earth’s surface
• This force always points towards the center of the Earth (downward). In a vacuum, all objects fall with the same acceleration

  Gravity
• A positive velocity shows that a body is moving upwards.
• A negative velocity shows that a body is moving downwards
• The value of gravity has to be negative all the time.
• In the free fall we assume that the initial velocity of the object is zero. Also, the final velocity and position are going to increase negatively because our initial position is zero. Gravity must be negative always.
• In vertical throw directed downwards, we assume that an object is launched vertically down, so the initial velocity is negative because it points to the ground.
• In the vertical throw directed upwards, an object is launched vertically up, so the initial velocity is positive and it will be decreasing little by little until a point where it is zero
• A projectile is a particle that moves near the Earth’s surface only by its weight (directed downward).
• In the equations for velocity of projectile motion, you can see that the velocity in the x-axis is constant, but in the y-axis first decreases and then increases negatively until it reaches the ground. This is due to gravity.
• The concept of range is also known as flight time in projectile motion.
• The angular displacement of a body shows us its amount of rotation. 
• Unit that is used a lot and that stablishes the relationship among the arch and the radius of a circle

  Radian
• The angular velocity is the angular displacement per unit of time
• If the angular velocity is in revolutions per second (rev/s) we call it angular frequency
• tangential velocity is the linear velocity that a body has when it is rotating at a certain angular velocity and which we also know the distance to the rotational axis, the radius
• Main field of mechanics that studies the motion of objects considering the causes of that movement. These cases involve different types of forces and energy.

  Dynamics
• Main field of mechanics that analyzes the causes of why objects are at a resting state, which is also called equilibrium.

  Statics
• One of the most influential scientists of all time since he formulated the fundamental laws of mechanics, for example the law of universal gravitation. He also invented mathematical methods in order to resolve his owns formulations and another of his scientific works was discovering the color spectrum of white light passing through a prism.

  Isaac Newton
• Force is a vector physical quantity that measures the intensity of the interaction between two or more objects.
• Contact force is the force in which an object comes in contact with another
• No-contact forces are produced by the interaction of a physical object with a vector field, like the gravitational field, the electric field or the magnetic field.
• It can be defined as the amount of matter that possess a body or as the physical scalar quantity that measures the resistance of an object for either acquiring motion, or to amend its motion condition (speed change).

  Mass
• Mass is a measure of the inertia that has an object, concept that is later explained in more detail in Newton’s Laws, being these the basis of mechanics.
• Also known as the inertia law, states that in the absence of external forces, a body at a resting state will always remain this way, or if it is in a state of motion at constant speed, it will continue in this state.

  First law
• Another allegation mentioned in Newton's first law indicates that while there are no forces that move them, the object will remain in this resting condition permanently.
• Also known as the law of motion, states that the acceleration that a body acquires is directly proportional to the resultant applied force and inversely proportional to its mass.

  Second law
• Newton's second law states that the acceleration that a body acquires is directly proportional to the resultant applied force and inversely proportional to its mass
• Also known as the action-reaction law, states that for every action force there is a corresponding a reaction force, which is equal in magnitude but with an opposite direction

  Third law
• A force is a physical quantity vector that describes the interaction between two objects that may be in contact or separated
• Is a distance force due to the interaction of a mass with the gravitational field produced by the earth. It is also called gravitational force of the object and has the direction of the gravitational field

  Weight
• Is a contact force due to contact between an object with a plane or a surface and this force has a direction that is perpendicular to the contact surface. It is represented with a cursive letter N/n. Its value can be in newtons or pounds.

  Normal
• A force manifested in every point of a rope due to the application of two equal forces on each end of the rope. Its value can be in newtons or pounds.

  Tension in a rope
• Diagram showing the forces acting on an object, where the direction of the forces depends on the characteristics of the type of forces applied. There is usually a figure or at least a writing about a case or problem of some object on which different forces are acting

  Free-body diagram
• When two surfaces are in contact, the friction forces oppose relative or impending motion. They are parallel to the contact surfaces and opposite two relative or impending motion
• Kind of friction without relative motion.

  Static friction
• Kind of friction with relative motion

  Kinetic friction
• The first equilibrium condition is that there is no resultant force. That means that the sum of all acting forces is equal to zero 
• If an object is at rest, it will remain at rest unless an external force makes it move. Which of Newton’s laws describes this situation?

  First Newton's law