Unit 02 Poster.pdf- Objects that change their position by different amounts each second must have changing motion.
- Motion can change in one of three ways: speeding up, slowing down, or turning. All of these are types of acceleration.
- By comparing an object's velocities at the beginning and end of a time period, we can measure the average amount of acceleration it experiences.
- Since acceleration is a comparison of two velocities (m/s) in a unit of time (s), the units for acceleration are meters/second/second.
- The units for acceleration are often simplified to m/s^2.
- The acceleration an object experiences must be caused by an unbalanced external force. This type of force is called a net force.
- Forces always have four characteristics: a cause, an object, a direction and a size, which we abbreviate CODS.
- In this class, forces are always measured in Newtons, which is a simplified form of the kg * m/s/s.
- If a force appears not to have a cause, it must not be a true force. An example of this is a centrifugal force.
- Forces come in two types: contact forces and field forces.
- Contact forces are pushes or pulls that are applied through a touch.
- Field forces are pushes or pulls that act at a distance. Gravitational, electrostatic and magnetic forces are all field forces.
- An analysis of the forces acting on an object can be accomplished using a free body diagram, on which all forces are represented as vector arrows drawn in the correct direction and to the correct relative size.
- Determination of the size and direction of a net force acting on an object can be made by adding the force vectors on a free body diagram.
- The acceleration an object experiences is directly proportional to the net force causing it.
- The acceleration that is produced by a net force must be in the same direction as that net force.
- A given net force acting on objects of different masses produces different accelerations. The acceleration an object experiences is inversely proportional to the mass of the object.
- NEWTON'S SECOND LAW OF MOTION summarizes points 12 and 13 in the following formula: F = ma.
- To use Newtons as the unit of measure of force, mass must be measured in kilograms and acceleration in meters/second/second.
- Weight is another name for the force of gravity between an object and the Earth.
- Mass and weight are very different concepts, but related through Newton's Second Law of Motion.
- Converting a mass (in kg) to a weight (in N) can be done by multiplying the mass by a constant 9.81 m/s/s.
- The constant in point 21 is the gravitational acceleration -- g -- which represents the acceleration experienced by all objects that fall freely near the Earth's surface.
- Contrary to popular belief, the mass of an object that falls freely does not affect the acceleration it experiences -- every object that is falling freely experiences an acceleration of g, regardless of its mass.