Gavin Ch. 4 Physics- Study of motion

Gavin   Ch. 4 Physics- Study of motion 

·       Describing Motion

·       Newton’s laws of motion

·       Conservation Laws in Astronomy

·       Force of Gravity

4.1

We describe motion with many different terms. 

Speed                    distance / time

Velocity                 tell both the speed and direction of an object

Acceleration         any change in velocity, both speeding up and slowing down

The acceleration of gravity on earth is 9.8 m/s

An objects momentum is the product of its mass and its velocity:  momentum = mass x velocity

The only way to change an objects momentum is to apply force.  Net force or overall force, represents the combined effect of all the individual forces put together.  A change in momentum occurs only when the net force is not zero.\

Mass is the amount of matter in your body, weight is the force that a scale measures when you stand on it.  Your mass is the same no matter where you are, but your weight can vary.

4.2

Newton’s laws of motion

Newton’s first law: 

An object moves at constant velocity if there is no net force acting upon it.  Newton’s law basically states that if a car is traveling along a flat, straight road it should keep going at the same speed forever unless another force is acting on it.

Newton’s second law

Fore = mass x acceleration (F=ma)

This law explains why Jupiter has more effect on asteroids and comets than smaller planets.

Newton’s third law:

For any force, there is always an equal and opposite reaction force.  This law is very important in astronomy, because it tells us that objects always attract each other through gravity.

 4.3 conservation laws in astronomy

Conservation of angular momentum: an object’s angular momentum cannot change unless it transfers angular momentum to or from another object.

Conservation of energy: Energy can be transferred from one object to another or transformed from one type to another but the total amount of energy is always conserved.

Types of energy:

Kinetic energy is the energy of motion

Radiative energy is the energy carried by light

Potential energy is stored energy.

Thermal energy represents the collective kinetic energy of the many individual particles moving randomly within a substance.  While temperature measures the average kinetic energy of particles.

Kelvin is the universal scientific measure of temperature.