Newton's Laws of Motion

• Newton's Laws are being tested

Free Body Diagrams

• Static equilibrium involves forces balanced at rest
• Dynamic equilibrium involves forces balanced while moving at a constant velocity

Newton's First Law

• An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force, this is called inertia
• Mass determines how much inertia an object has
• Inertia is a property of matter that describes an object's resistance to acceleration
• Force is not inertia
• Inertia causes an object in motion to remain in motion and a stationary object to remain stationary
• In space travel, objects travel in a straight line unless a force acts upon them

Newton's Second Law

• Fnet = m * a describes how an object's motion changes when a force is applied
• Fg = m * g can also be used, where g = 9.81 m/s²
• Use a free body diagram to find Fnet
• Acceleration has an inverse relationship with mass
• Acceleration has an equal relationship with force

Newton's Third Law

• Every action has an equal and opposite reaction, these occur in pairs with equal magnitude and opposite direction

Rocket Action and Reaction

• Taking off involves the rocket pushing down on the fuel exhaust (action), and the fuel exhaust pushing up on the rocket (reaction)
• Moving through space involves the rocket pushing down on fuel exhaust (action), and fuel exhaust pushing up on the rocket, accelerating it in space (reaction)

Apollo 13 Movie

• The film follows three astronauts: Jim Lovell (commander), John Swigert, and Fred Haise
• The astronauts attempted to land on the moon, but were unable to due to an oxygen tank bursting
• The crew had to do a free trajectory return and landed safely, but they never made it to the moon
• The astronauts are pushed back on their seats because as the ship accelerates forward, the astronauts accelerate backwards due to inertia
• They accelerate or exert a force when they burn the engine
• The rocket pushes down on the fuel exhaust, and the fuel exhaust pushes up on the rocket causing the rocket to accelerate away from the Earth

Newton's Second Law Lab

• The experiment tested how different amounts of mass affected the acceleration of a cart
• The amount of mass was increased by 0.5kg increments, and then the cart was released and the acceleration recorded
• The independent variable was the mass of the cart (kg)
• The dependent variable was the acceleration of the cart (m/s²)
• The controlled variable was applied force (about 0.5N, mass hanger plus mass on hanger = 50g)
• The relationship between the mass of the cart and the acceleration of the cart is inverse, since as mass increases, acceleration decreases
• The relationship and graph between net force and acceleration is linear: Fnet = m * a

Net Force/Applied Force (Controlled Variable)

• If net force increases, the acceleration of the cart increases, since acceleration has an equal relationship with force
• If net force decreases, the acceleration of the cart decreases, since acceleration has an equal relationship with force

Mass on the Cart (Independent Variable)

• If mass increases, the acceleration of the cart decreases, since acceleration has an inverse relationship with mass
• If mass decreases, the acceleration of the cart increases, since acceleration has an inverse relationship with mass
• If the applied force/controlled variable increases, the further the inverse curve moves away from the axis
• If the applied force/controlled variable decreases, the closer the inverse curve moves to the axis

Explore Newton's Laws. Understand inertia, force, and acceleration. Learn how forces affect objects at rest and in motion and their relationship as defined by Newton.