Matter has has units ofis a measure of is has units of Definition: Mass Volume kgInertia Amount of space something occupies Resistance to changes in motion cm 3, liters

Inertia is a property of matter is mass is measured in kg is not dependent on the motion of the object As mass increases, inertia increases As mass decreases, inertia decreases

Newton’s Laws help explain and predict the workings of the mechanical world. Newton’s 1 st Law (N1L) – a.k.a. Law of Inertia A force is required to change the motion of an object

A change in motion could be:  speeding up  slowing down  stopping  starting  changing direction These are all examples of acceleration

 Objects will continue moving in straight paths at the same speed unless acted upon  In real world we don’t see this because of friction (a force that opposes motion)  Objects at rest will not move unless forced

According to N1L, a change in motion will only occur when a force causes it If no change in motion then either: 1. no forces are acting on it or 2. all forces cancel each other out (F net = 0)

When all forces cancel each other out F net = 0 Example F net = F 1 – F 2 = 0 **This object may be motionless or moving with constant speed (speed is unchanging). F2F2 F1F1