ForcesUse the force Luke!

Forces

• Difference between mass and weight:

• Weight is the force you put on the Earth: In the English system we use lbs. In the Metric system we use Newtons.

• Mass is how much matter you are made up. We use kilograms

Force• Pressure = Force / Area

• The bigger the area, the less the pressure, with the same force

Force

• What is the pressure when an object with an area of 100m² is applied with a force of 100N.

• The unit of this is called a Pascal, or Pa

Force

• Friction is a force that always works against your motion. It decreases velocity.

• Types of friction: liquids, air resistance, rough floors, etc

• There are two types of friction: static friction and sliding friction

Force

• Static friction: the force that opposes the start of motion. When the magnitude of your push on the box is greater than the maximum value of static friction, the box moves.• Kinetic friction: The force between

surfaces of relative motion. This force is less than that of static friction.

Force

• The coefficient of friction can usually be found with the following equation:

Where μ is the coefficient of friction. FN is the normal force and Ff is the frictional force. This formula can be used for both types of friction

Force

• The free-body diagram: This is a way to put all of the forces together on a box to see where the motion is occurring:

• Important forces to graph:Normal force, Friction force, Weight force, Applied force

Force

• Example pg 99

• Then example on pg 126. If you don’t have your chapter 6 packets, grab a book

Force

• Group activity on free body diagrams and the coefficient of friction

Force

• Homework

• Pg 95 #8, pg 100 #10a,10b, pg 102 #13,16 (use free body diagrams for this one and F=ma) and pg 126 #26 (you must attempt for full credit, +2 Extra Credit points for a correct answer)

• HW due 10/1/15