Newton’s First Law of Motion An object at rest tends to stay at rest and an object in motion tends to stay in motion (with the same speed and in the same direction) unless acted upon by an unbalanced force. This tendency to resist changes in their state of motion is described as INERTIA

Newton’s 2nd Law F = mass x acceleration F = m a The acceleration of an object is directly proportional to the net force acting on the object and is inversely proportional to the mass of the object. In other words: F = mass x acceleration F = m a

F m a Newton’s 2nd Law Units Measurement Unit Force N Mass kg Acceleration m/s2

Newton’s 3rd Law of Motion Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. Action-reaction Force Pairs For every action there is an equal and opposite reaction

Action-Reaction Forces come in pairs If you push on a box, the box pushes back on you In the opposite direction

Example #1 A baseball pushes a glove to the left What is the reaction force?

Example: Newton’s 3rd Law Ex: Bird uses its wings to fly. Action: Wings push air downwards Reaction: Air pushes the bird upwards Equal Force in opposite directions

Example: Newton’s 3rd Law Ex: Interaction between a baseball and bat Action: Baseball forces the bat to the left Reaction: The bat forces the ball to the right Action-reaction Force Pairs

Example: Newton’s 3rd Law Ex: Interaction between tires on car and road Equal Force in opposite directions Action-reaction Force Pairs For every action there is: an equal (in size) & opposite (in direction) reaction

Mass vs. Weight MASS is a measure of the amount of matter in an object Mass will not change as you move from place to place WEIGHT is a measure of the gravitational force exerted on an object (the force with which Earth’s gravity pulls on a quantity of matter) The force varies from place to place Ex: Weight of an object will be different on Earth than on the moon

Fg vs. Mass Lab Purpose: To graphically and mathematically determine the relationship between Fg and mass of an object. What will be our independent variable? What will be our dependent variable? How will we measure force? How will we measure mass?

Post-Lab Results Mass (kg) Force of Gravity (N) Calculated Slope