NEWTON’S LAWS

Newton’s 1st Law of Motion Object in motion stays in motion And Objects at rest stay at rest Until they are acted upon by unbalanced forces.

Law of Inertia is another name for Newton’s 1st Law Tendency for an object to stay at rest or moving in a straight line at a constant speed. The mass (m measured in kg) of an object determines its inertia Inertia comes from the Latin word meaning lazy.

Unit of Force Unit of mass is kg Unit of Acceleration is m/s/s 1 kg · 1 m/s/s = 1 kg · m/s/s = 1 Newton (N) Resulting in Force unit called a Newton (N)

Newton’s 2nd Law or the Law of Acceleration Force = Mass· Acceleration F = ma Weight (pull of gravity) is a commonly measured force, calculated by F=mg, g is the acceleration due to gravity 9.8 m/s2

Newton’s 2nd Law of Motion The greater the mass of an object, the greater the force required to change its motion.

Newton’s 2nd Law of Motion The greater the acceleration of an object, the greater the force required to change its motion.

Your Turn! How much force is needed to accelerate a 1,300 kg car at a rate of 1.5 m/s2? To solve this: F = m a or = 1300Kg x 1.5m/s2 F = 1950 N

Newton’s 3rd Law of Motion Forces always work in pairs For every action force there is an equal and opposite reaction force.

Newton’s 3rd Law of Motion All forces come in action-reaction pairs Ex: feet push backward on floor, the floor pushes forward on feet

Newton’s 3rd Law of Motion Rocket and Jets- walls of the fuel compartment push backward on igniting gases, gases push forward on the fuel compartment (and the rocket) so it rises.

Newton’s 3rd Law of Motion Rowing a boat Name the Action Reaction pair of forces? Action: Oar pushes water back. Reaction: water pushes boat forward.

Friction A force that acts in a direction opposite to the motion of two surfaces in contact with each other.