WHAT IS FORCE. A force is a push or a pull WHAT IS FORCE? A force is a push or a pull. Forces (unbalanced) CAUSE objects to accelerate. Ex. Pull Open a door Forces occur when objects interact with each other.

Forces Forces are represented by arrows. The head of the arrow shows the direction of the force The width/length of the arrow shows the strength of the force Large force pushing right Small force pushing left

Forces- Two Main Categories Contact Forces Action-at-a-Distance Forces Frictional Force Gravitational Force Tension Force Electrical Force Elastic Force Magnetic Force

Contact Forces Tension Force: is force experiences by a wire or a rope when it is pulled at either end. Friction Force: works to slow down or stop motion due to surfaces rubbing against each other. Elastic Force: is exerted when a spring like object such as a trampoline restores itself to normal shape after it has been compressed or stretched.

Action at a distance forces Gravitational Force: is the force of attraction between objects because they have mass. The force depends on both the masses and the distance. Electrostatic Force: or static electricity. Causes pushing and pulling forces. All matter is composed of electrically charges particles (+ or – charged). Static electricity is the excess of + or – charges. Charges that are the same repel and charges opposite attract Magnetic Force: acts on certain metals and compounds such as iron, nickel, and cobalt. Natural magnets including earth and electromagnets have a field around them, that can exert pushing and pulling forces.

Difference between Mass and Weight Mass: amount of matter in an object. (never changes) Weight: depends on gravity. It is the amount of force on an object due to gravity. The measuring unit of force is Newtons (N)

You got 2 minutes to make sure your group is ready to present your force topic

Measuring Force Force meters are equipped with a spring or similar elastic device that stretches or compressed in response to being pulled or pushed. https://www.youtube.com/watch?v=AFu1advEnhw Frictional force https://www.youtube.com/watch?v=bOjgpbZ8VpM

The lab Using the handout I gave you, you are going to get a partner and work together to complete the lab. I have set up stations for each type of force and left materials. Part 1: I want you to try and figure out how these materials relate to the force and how they may be used. Bring the chart you made last class with you for reference. Part 2: Using the spring scales, test out some different frictional or gravitational forces. Record what you used, and the forces you found. Part 3: You now get to come up with your own lab using some of the material in the class. Pose a question you want to answer about a type of force and create a lab around it.

Forces Lab Part 1: Description: describe the force Comments: From what items are on the table, how did you observe or use this force? Part 2: Gravitational: Write down the weight of the block and then the force on the scale. Frictional: write down the amount of blocks you pulled, or types of blocks you pulled and the amount of force it took to move them. (in Newtons)

UNBALANCED FORCES Unbalanced forces always cause a change in motion       Large force pushing the ball towards the right Smaller force pushing the ball to the left

Two forces balance each other if they are of equal  magnitude/strength and act in opposite directions. Net force = 0

Newtons First law of motion An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.  

Balanced Forces Since these two forces are of equal magnitude and in opposite directions, they balance each other. The book is said to be at equilibrium. 

Now consider a book sliding from left to right across a tabletop Now consider a book sliding from left to right across a tabletop. Balanced or unbalanced?

Balanced or Unbalanced?

Inertia = the resistance an  object has to a change its state of motion. The more mass an object has, the more inertia it has …the more tendency it has to  resist changes in its state of motion.

http://www.youtube.com/watch?v=Q0Wz5P0JdeU

How many forces are acting upon a suit case when it is picked up and why?

http://gbhsweb.glenbrook225.org/GBS/science/phys/Class/newtlaws/u2l2b.html#grav http://www.physicsclassroom.com/class/newtlaws/u2l1d.cfm