- Slides: 14
Newton’s Laws Aim: How do Newton’s Laws affect moving objects?
Newton’s First Law 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
Which has more Inertia? 100 m/s Inertia = Mass; Speed has NO affect on Inertia!
I w o kn e. I n h Yea ped o o it! skip l get t ’l We Newton’s Third Law For every action there is an equal and opposite reaction Action Reaction
If the sumo wrestler slams into the kid with 100 Newtons of force, how much force does the kid hit the sumo wrestler? 100 N For EVERY action there is an EQUAL and OPPOSITE reaction
! e e S To a! y ld Newton’s Second Law 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. 25 th 1642 – March 20 th 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 20 kg crate at 2 m/s 2?
Example #2 A 1200 kg car slows to a stop in 3 seconds when the brakes apply a force of 2. 0× 104 N. How fast was the car going?
Example #3 The combined mass of a child on a bike is 75 kg. If the child rides at a constant velocity, what net force acts on the child? 0 N
If something is either “STATIONARY” -OR“MOVING AT A CONSTANT SPEED/VELOCITY” Velocity does NOT CHANGE Acceleration = 0 m/s 2 Net Force = 0 N 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 1 st Law of Motion • Describe Newton’s 2 nd Law of Motion • Describe Newton’s 3 rd Law of Motion • How do you calculate force? • What are the units force?