Aim: How do Newton’s Laws affect moving objects?

Newton’s First Law “Law of Inertia” An object in motion (or at rest) will stay in motion (or at rest) unless acted on by an unbalanced force “Law of Inertia” Inertia – The resistance of an object to change in its motion; directly proportional to the objects MASS

Inertia = Mass; Speed has NO affect on Inertia! Which has more Inertia? 100m/s Inertia = Mass; Speed has NO affect on Inertia!

Yeah I know I skipped one. We’ll get to it! Newton’s Third Law Yeah I know I skipped one. We’ll get to it! For every action there is an equal and opposite reaction Action Reaction

For EVERY action there is an EQUAL and OPPOSITE reaction If the sumo wrestler slams into the kid with 100 Newtons of force, how much force does the kid hit the sumo wrestler? 100N 100N For EVERY action there is an EQUAL and OPPOSITE reaction

Newton’s Second Law See! Told ya! The acceleration of an object is directly proportional to the force exerted on it but inversely proportional to the object’s mass Mass Units: Kilograms (kg)

Sir Isaac Newton Dec. 25th 1642 – March 20th 1726 Invented Calculus & the Reflecting Telescope Believed to have died a virgin due to being deeply religious and wasn’t “subject to frailties of man”

Example #1 How much force is required to accelerate a 20kg crate at 2m/s2?

Example #2 A 1200kg car slows to a stop in 3 seconds when the brakes apply a force of 2.0×104N. How fast was the car going?

Example #3 The combined mass of a child on a bike is 75kg. If the child rides at a constant velocity, what net force acts on the child? 0N

Velocity does NOT CHANGE If something is either “STATIONARY” -OR- “MOVING AT A CONSTANT SPEED/VELOCITY” Velocity does NOT CHANGE Acceleration = 0m/s2 Net Force = 0N EQUILIBRIUM

Weight The amount of force gravity pulls on an object ALWAYS STRAIGHT DOWN! Mass Units: Kilograms (kg)

WEIGHT ≠ MASS Mass and Weight are NOT THE SAME Mass is measured in KILOGRAMS (kg) Weight is measured in NEWTONS (N) However, they are RELATED More mass  More weight Stronger gravity  More weight Generally, MASS remains CONSTANT

SUMMARY Describe Newton’s 1st Law of Motion Describe Newton’s 2nd Law of Motion Describe Newton’s 3rd Law of Motion How do you calculate force? What are the units for force?