Motion & Forces

Force• A push or

a pull*Cause an

object to start moving, stop moving, or change direction

Unbalanced Force

• Cause an object to start moving, stop moving, or change directions

• Unbalanced forces will change an object’s motion

Unbalanced ForcesNet Force = the overall

force on an object after all the forces on an object are added up

1 2 1

1 2 1

3

12

Balanced Forces• Equal forces

acting on each other in opposite directions

*Balanced forces acting on an object will not change the objects motion

1 0 1

1 0 1

An object at rest will remain at rest and an object that is moving at a constant velocity will remain at a constant velocity unlessacted upon by an unbalanced force.

Inertia-the tendency of an objectto resist change in its motion.Newton’s 1st Law of Motion is also called the Law of Inertia.

Inertia• Force is needed to

change the motion of an object. Every object resists any change to its motion. This change is called inertia. The tendency of an object to resist change in its motion

Ex. If you are not wearing a seat belt when a car crashes inertia continues to carry you forward

What affects Inertia?

• Mass the greater the mass the greater the inertia

Question what has greater inertia a Honda Civic going 30 k/ph, or a Truck at the same speed?

““Friction””The force that one surface exerts on another when

the two rub against each other.

Depends on 2 factors

1) The two surfaces involved

2) How hard are the surfaces pushing against each other

Types of Friction

• Sliding – when solids slide over each other

• Rolling - when an object rolls over a surface

• Fluid- objects moving through fluids (liquid or gases)

Weight vs. Mass• Weight is a measure

of the force of gravity on an object, mass is a measure of the amount of matter in an object

• You have the same mass on the Moon as Earth, but different weights

Gravity

• Gravity is a force between any two objects, the force of gravity is related to the mass of the objects, and their distance from each other

Force in Fluids

• Force is applied to a fluid causing pressure increase in a fluid

• The heart applies pressure to the blood forcing it through your vessels, blood flow in the body requires force