Force

• a push or a pull• a force gives energy to an object causing it to…– start moving, stop moving, or change direction

• the unit of measurement is Newtons (N)– used to be a kg(m/s2)– this is about ¼ pound

• forces in the same direction are added to make the resulting force stronger

• forces in different directions are subtracted which makes the resulting force weaker– if these forces are equal, they are balanced forces

Types of Forces• Contact Forces: the objects involved are touching

each other and friction is created– friction is a force that is in the opposite

direction to the moving object and therefore, slows it down

– 3 types of friction• rolling• sliding• fluid – this is caused by an object moving

through a liquid or a gas

• Non-contact forces: objects are pushed or pulled without being touched– gravity

– electricity

– magnetism

F = Forcem = massa = acceleration

F = ma or F = m·a or F = m x a or F = m(a)

Force formula

Two ways an object has force and how to use the force formula

1. Object is accelerating.– if it is rolling, flying, and/or sliding it has a

force– think of a car hitting you

2. Object is NOT moving (more on this later)– this is a result of gravity– think of a car on top of you!

Example problem• A rocket has a mass of 3.5 kg and an acceleration

of 3.0 m/s2. What is the rocket’s force?

m=3.5kg F=ma a=3.0m/s2

given formula set up problem answer w/ unit of measurement

A kg(m/s2) is the same as a Newton so 10.5 N would be the same, but simpler.

3.5kg(3.0m/s2) 10.5 kg(m/s2)