Newtons’ 1st LawPrinciples of Physics - Foederer

Matter

hashas

has units of is a measure of

is

is

has units of

Definition:

Definition:

Mass Volume

kg InertiaAmount of space something occupies

Resistance to changes in motion

cm3, 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 increasesAs mass decreases, inertia decreases

Newton’s 1st LawNewton’s Laws help explain and predict the

workings of the mechanical world.

 

Newton’s 1st Law (N1L) – a.k.a. Law of Inertia

A force is required to change the motion of an object

Newton’s 1st LawA change in motion could be: speeding up slowing down stopping starting changing direction

These are all examples of acceleration

Newton’s 1st Law 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 (Fnet = 0)

When all forces cancel each other out Fnet = 0

Example

Fnet = F1 – F2 = 0

**This object may be motionless or moving with constant speed (speed is unchanging).

F2 F1