Motion and Forces

1. Newton’s Laws of Motion
   1. Second Law (F=ma)- An unbalanced force acting on an object causes an acceleration which is directly proportional to the force and in the direction of the force. The acceleration will vary directly with the magnitude of the force and inversely with the mass of the object.
   2. Third Law- If one body exerts a force on a second body, the second body exerts a force equal in magnitude and opposite in direction on the first body.
2. Gravitation is a universal force that each mass exerts on any other mass.
   1. The strength of the gravitational attractive force between two masses is proportional to the masses and inversely proportional to the square of the distance between them.
   2. Every object experiences this force of attraction, but, when the masses are relatively small, the forces are small.
3. Electric force is a universal force that exists between two charged objects.
1. If two objects have an excess of electrons, (and therefore have a negative charge) they will repel each other. However, if one object has an excess of electrons, and the other has a deficit, they will attract each other.
2. The electric force between two charged objects is proportional to the quantity of the charge and inversely proportional to the distance between them.
4. The forces that hold the nucleus of an atom together are stronger then electromagnetic forces and significant amounts of energy are released during nuclear change.
   1. Nuclear forces are strongly attractive and much larger in relative magnitude than electrostatic and gravitational forces.
   2. Nuclear fission and nuclear fusion are two special kinds of nuclear reactions in which energy release is exceptionally large.
5. Electricity and magnetism are two aspects of a single electromagnetic force.
   1. When a charge moves through a specific conductor, a magnetic field is produced.
   2. When a conductor moves across externally established magnetic lines of force, a current is induced in the conductor.

Energy Transformations

1. The total amount of energy in a closed system is constant. (Conservation of Energy.) Within a closed system, energy can change from one form to another but the total amount of energy always remains constant.
2. Mechanical energy is either kinetic or potential.
   1. Potential energy is energy that is stored. Potential energy depends on the position of the object within the system.
   2. Kinetic energy is the energy of the object due to its motion. The faster an object moves, the more kinetic energy it has.
   3. Whenever mechanical energy is transformed, some heat is dissipated and therefore is unavailable for use.
3. Electromagnetic waves result when a charged object is accelerated or decelerated. Electromagnetic waves include radio waves, microwaves, infrared waves, visible light, ultraviolet radiation, x-rays, and gamma rays.
   1. Electromagnetic waves are distinguished from each other by their wavelengths.
   2. The sun radiates the full spectrum of electromagnetic waves.
   3. The higher the frequency of the waves, the more powerful the electromagnetic energy.
4. Energy can travel as a wave or particle.
   1. Heat and sound travel as waves.
   2. Electricity travels as particles.
   3. Light exhibits a dual nature
5. In some cases energy requires a medium in which to travel
6. Waves and particles exhibit the same properties and some exclusionary properties.
7. The properties of a medium have an affect on the movement of energy.