Power point summary unit 5 In textbook Chapters 10 and11

Distance vs. Displacement Distance Definition: The length of a path between two points remember to use SI Units (meters) Displacement Definition: The position change and direction of an object The straight line between your starting point and the finish point

Distance = = 420 Displacement = 140 Right

Speed vs. Velocity Only one difference Speed is the distance an object moves in a given amount of time s = d/t (unit = m / s) The car speedometer shows you traveling at 35 m / s Velocity is speed with a direction v = d/t(unit = m / s) A man walked 5 miles east from his house every morning to get the mail

Changing Velocity Velocity can change in one of two ways: 1. A change in speed 2. A change in direction

Instantaneous vs. Average Instantaneous Speed or Velocity is the distance divided by the time at a given moment Average Speed or Velocity is the total distance divided by the total time

Speed (distance vs. time) Always label time in the x axis Time (sec) Distance (meters)

Increasing velocity Distance (meters) Time (s)

Constant velocity Time (sec) Velocity (m/s)

Acceleration Acceleration – change in velocity per unit of time a = Δv or v f – v i t t Remember: Like velocity, Acceleration includes direction Acceleration can change by speed or by direction

What is a Force A Push or pull that acts on an object Units is a Newton (N) Examples of force – The wind – Any sport – Car crashes

Newton’s First Law of Motion An object will remain at rest or constant velocity unless a force acts upon it.force – A force is a push or a pull. INERTIA: an object’s resistance to a change in motion. Inertia is dependent on an objects mass. INERTIA

Newton’s Second Law of MotionLaw When a net force acts on an object, the object to accelerate in the direction of the net force F = ma

2 nd law What does F=ma really mean Mass and acceleration are proportional to the force – If mass or acceleration increases – the force will also increase – If the force decreases - mass or acceleration decreases – This is called a directionally proportional

What is a Newton Unit of force abv = N N = kg x m/s 2

Gravity – Law of GravitationLaw of Gravitation The attractive force of two objects upon each other Affected by: 1. Distance between the objects 2. Mass of the objects

Why??? Would you weigh more on Earth or on the moon? Why do you think you weigh more on Earth than on the moon? The moon is 1/6 the size of earth so the moon’s gravity is… 1/6 the gravity of the earth

Mass Vs Weight Mass – constant, is defined as the amount of matter an object has – Size does not determine mass Weight – the result of gravity pushing down on you.

Mass Vs Weight

Mass Vs. Weight Mass - the amount of matter an object has Weight – determined by gravity Formula = same as force F w = m * a g F w = Force of weight (Newtons) m = mass (Kilograms) a g = acceleration due to gravity=9.8 (meters/sec 2 )

Newton’s 3 rd LawLaw For every action there is an equal and opposite reaction When one object exerts a force on another object, the second object exerts a force of equal strength in the opposite direction on the first object. (Action / Reaction)