Newton’s Laws of Force Chapter 2 Section 3

Force and Motion What is a Force? What is a Force? A push or a pull A push or a pull pull open a door pull open a door push on a chair push on a chair

List all the forces that you exert in a day List all the forces that you exert in a day push, pull, stretch, squeezing, bending, falling push, pull, stretch, squeezing, bending, falling

Effect of Forces on Objects What happened to the objects that you applied a force to on your list? What happened to the objects that you applied a force to on your list? Change speed Change speed change direction change direction change size change size

Maybe the force didn’t change anything Maybe the force didn’t change anything sitting on you chair sitting on you chair playing tug of war playing tug of war those forces are said to be balanced forces those forces are said to be balanced forces forces that are equal is size and in opposite direction forces that are equal is size and in opposite direction

Maybe your force caused a change in direction Maybe your force caused a change in direction pushing on a friend in the hallway pushing on a friend in the hallway Maybe your force caused a change in speed Maybe your force caused a change in speed pushing of a bike pedal pushing of a bike pedal

These forces would be unbalanced and there would be a net force These forces would be unbalanced and there would be a net force A net force will cause a change in velocity (either speed or direction) A net force will cause a change in velocity (either speed or direction)

Inertia and Mass Consider an ice skater gliding across the ice Consider an ice skater gliding across the ice constant velocity until hits the wall or push off with her foot again constant velocity until hits the wall or push off with her foot again

This demonstrates inertia This demonstrates inertia an object stays in motion or an object stays at rest until a net force act on the object an object stays in motion or an object stays at rest until a net force act on the object Does a VW and a semitruck have the same inertia? Does a VW and a semitruck have the same inertia? What determines the inertia? What determines the inertia?

Mass The amount of matter in an object The amount of matter in an object Units of kilograms Units of kilograms

Newton’s First Law of Motion Also called the Law of Inertia Also called the Law of Inertia explain by using Newton’s first law why you should wear a seat belt explain by using Newton’s first law why you should wear a seat belt Inertia says that an object should keep moving so why does it slow down and stop? Inertia says that an object should keep moving so why does it slow down and stop?

Measuring Forces Spring scales measure the forces (weight) applied by object Spring scales measure the forces (weight) applied by object Force is measured in units Newtons, N Force is measured in units Newtons, N