Motion

Event that involves a change in the position or location of something. Definition Event that involves a change in the position or location of something.

Motion is Relative Relative – it is described compared to a REFERENCE POINT

Scalar Quantities Show magnitude [amount] only Speed, time, temperature

Vector Quantities Show magnitude and direction Velocity, acceleration, force May be graphically represented Arrows

Speed Average Speed Comparison of time and distance A scalar quantity [magnitude only] Distance traveled per unit time S = d / t T = d / s D = s x t

Speed Instantaneous Speed Speed at any instant

Speed Constant Speed Speed that does not change Instantaneous speed that does not change

Velocity Speed AND direction A vector quantity [magnitude & direction]

Acceleration A change in velocity Speeding up Slowing down Positive acceleration Slowing down Negative acceleration Deceleration Changing direction

Forces – Chapter 12 Pushes or pulls May cause acceleration [changes in motion] Measured in Newton (N) F=ma

Balanced Forces All forces acting on an object are equal There is no motion

Unbalanced Forces All forces acting on an object are not equal One or more force is stronger than others Motion occurs

Balanced or Unbalanced Forces?

Net Force The sum of all forces acting on an object A net force of 0 No motion A net force of more than 0 Motion occurs

Friction Force that slows down motion Air resistance creates friction in most situations

Air Resistance Opposes the motion of objects that move through the air. Force of air resistance Force of air gravity

Gravity Force that attracts all objects toward each other More mass = more gravity Acceleration due to gravity is 9.8 m/s/s All objects accelerate at the same rate gravity video elevator video

Gravity What is Gravity? It is an attractive force between two objects that depends on the masses of the objects and the distance between them. Force of Earth’s Gravity F = m*g Force of gravity(N) = mass(kg) * acceleration of gravity(m/s2)

Newton's Laws Describe motion and changes in motion

First Law of Motion Law of inertia Objects at rest [not moving] will not begin to move until a force acts on them Objects in motion will not stop moving until a force acts on them Objects with more mass have more inertia Bigger objects are harder to start and stop Eureka Inertia

Second Law of Motion Law of acceleration A force is needed to change motion Objects accelerate in the direction of the force The more force applied, then more acceleration The more mass an object has, the more force is needed to accelerate the object Eureka Mass

Newton’s Second Law of Motion States that the acceleration of an object is in the same direction as the net force on the object. Net Force Equation F = m x a Force (Newton) = mass (Kg) x acceleration (m/s2)

Third Law of Motion Law of action-reaction Forces occur in pairs The forces are equal and opposite One force is an action force The other force is a reaction force The forces act on different objects

bill nye momentum

Momentum Every moving object has momentum. It is the amount of force required to change its motion. momentum (kg m/s) = mass (kg) × velocity (m/s) p = m × v If a car has a mass of of 1100kg and is traveling at 25m/s what is its momentum?