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.

Bell Work 1/26/10 Please answer #1-4 on page 47 in the book on your yellow bell work sheet.

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 formula acceleration = 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.

Bell Work 1/27/10 – choose the correct word to fill in the blanks: force, inertia, motion, net force, Newton’s first law, unbalanced force 1. _______ is the change of position over time. 2. The overall force acting on an object when all forces are combined is called _____ 3. A force that can change the motion of an object is called a(n) ________. 4. A(n) _______ is a push or a pull. 5. Objects at rest remain at rest, and objects in motion remain in motion at the same velocity, unless acted on by an unbalanced force. This statement describes ____. 6. The resistance of an object to a change in speed or direction is called_______.

Bell Work 1/27/10 Fill in the blanks 1. If you increase the force on a box, it will have _______ inertia. 2. You push two chairs in a straight line with the same force. One chair is more massive than the other. The more massive chair will have _______ acceleration. 3. Any force that is keeping an object moving in a circle is known as ______. 4. Acceleration is ________.

Centripetal force – any force that keeps an object moving in a circle

Force Notes 2.3 Newton’s Third Law – states that for every action there is a reaction