Newton

1
Newtons Laws
2
Motion

• Velocity describes motion.
• Speed and direction
• At rest no velocity
• Planets have a velocity at each point in their
  orbits.
• Circle or ellipse

• Acceleration is the change in velocity.
• Change in speed
• Change in direction
• Orbits require acceleration.
• Changing direction circle
• Changing speed ellipse

3
Elliptical Motion

• Velocity points along the motion.
• Red arrows
• Acceleration points in the direction of change.
• Blue arrows

y
x
4
Force

• Force is
• A push or pull on an object.
• A property with magnitude and direction.

• Some forces
• Fundamental forces
• Electricity and magnetism
• Nuclear forces
• Gravity
• Contact forces
• Friction
• Tension
• Normal forces

5
Dynamics

• Ancient scientists looked to the natural
  properties of objects to describe motion.
• Newton defined motion based on forces acting from
  outside an object.
• Motion from external forces
• Three laws for motion

6
First Law Law of Inertia

• An object continues at rest, or in uniform motion
  in a straight line, unless a force is imposed on
  it.
• This describes constant velocity, including zero.
• No change means no net force, and vice versa.

no force
rocket
constant velocity
7
Mass

• Matter has substance.
• Solids, liquids or gases
• Subatomic particles
• Planets and stars
• Mass measures the amount of matter.
• Standard kilogram
• 1 kg 1000 g
• 1 hydrogen atom 1.66 x 10-27 kg

8
Second Law Law of Acceleration

• The change in motion is proportional to the net
  force and the change is made in the same
  direction as the net force.
• Net force gives rise to acceleration.
• Force mass x acceleration.
• 1 newton (N) 1 kg m/s2

Final velocity changed by the force
Rocket has mass
Initial velocity
Force becomes acceleration
9
Third Law Law of Reaction

• For every action there is an equal and opposite
  reaction.
• Forces between two objects act in pairs.
• F12 -F21

reaction force acts on the rocket
rocket
rocket and gas are both affected
hot gas is forced out