Motion and Forces

Chapter 2

Bell Work 1/21/10

Copy each of these statements onto your bell work sheet. Then decide if they are true or false. If false correct them.

1. Speed includes direction, while velocity does not.

2. A moving object covers the same distance in less time if its velocity is greater.

3. Acceleration measures only change in speed.

Bell Work 1/22/10

Please begin working on your foldable or PowerPoint

On your bell work sheet write down “working on project” for today

Bell Work 1/25/10

Please begin completing the Map Practice Packet. Write your answers for each question on your yellow bell work sheet for today. PLEASE DO NOT WRITE IN THE PACKET

Force 2.1 Notes forces occur when one

object pushes or pulls on another object

We say that one object exerts a force on another object to cause it to accelerate.

Describing Forces forces are describe

according to: strength and direction

Two types of Forces Unbalanced Force

two forces acting in the same direction

OR

One stronger force acting in the opposite direction of a weaker force.

*Unbalanced forces cause an object to accelerate!

Balanced Force equal forces acting in

opposite directions

* balanced forces will NOT change the object’s motion!

Newton’s First Law An object at rest will

remain at rest unless acted upon by an unbalanced force!

continued

An object moving at constant velocity will continue moving at constant velocity unless acted upon by an unbalanced force.

Law of Inertia Newton’s first law is often

referred to as the Law of Inertia.

Inertia is a property that describes an object’s resistance to changes in motion. if an object is moving,

inertia keeps it moving. if an object is at rest, inertia

keeps it at rest.

Mass – is the amount of matter in an object.

Mass is a measure of inertia. the more mass an object

has the more inertia it has. This means it will take more force to get it to accelerate.

the opposite is also true: less mass, less inertia, less force.

mass is measured in kg.

How are mass and inertia related?

The more matter in an object, the harder it is to get the object to accelerate or you could say the harder it is to overcome the object’s inertia.

Force 2.2 Notes Newton’s Second Law of

Motion Explains a relationship

between force, mass and acceleration

Often expressed as: force = mass x acceleration

Simply stated: An object’s acceleration depends on the mass of an object and the strength and direction of the force acting on it.

Force = mass x acceleration

Units: acceleration – m/s/s mass – kg force – kg x m/s/s or

Newton (N)

Rearranging the Force Equation

To calculate mass:

Mass = ___force___

acceleration

To calculate acceleration:

Acceleration = force

mass

Using the formulaacceleration = force/mass

We know the following: as force increases,

acceleration increases. as mass increases,

acceleration decreases.

to get an object to accelerate, you must increase force or decrease mass.