#11 10/15 FORCES combining

Transcription

1 #11 10/15 FORCES combining Combined Forces When Force A and B are equal When Force A is greater than B When Force B is greater than A What do you think will happen to the scarf in the middle? Predict it s motion Force A Describe the motion of the object (scarf) in the middle of the rope. Force B Was your hypothesis correct?

2 Materials Needed Today Please take these materials out of your backpack. Pencil Blank paper for notes *ALL LATE WORK IS DUE BY THE 28 th!! Hot Sync Wednesday 10/23/13 Answer the following questions in complete sentences on the hot sync worksheet. Get out your hotsync to fill in after the video.

3 What are Forces?

4 Hot Sync Think about the video of all the accidents. Why did the two kids on the ice fall? What force was acting on them? Would they have fallen the same on regular land? What is the difference? Why did little kid on the slide fall when the second kid hit her? Who exerted the greater force? The kid who fell or the kid who hit the other? Recall when the men were pushing the BIG branch back and let go sending the guy flying why did this happen?

5 Write on the back of your worksheet: Conclusion: In conducting this experiment, we found that when two opposing forces on an object are equal, the object will when two opposing forces on an object are unequal, the object will. HINT: The blanks should be filled with your description of the motion of the object; if it moves, which direction does it move?

6 Lets answer these questions as a class Write under your conclusion: Does an object have force? Explain Is force an interaction between two objects? Explain Will the motion always be in the direction of the greater force? Explain

7 FORCE When more than one force acts on an object, the combined effect is caused by the sum of all applied forces. A push or a pull on an object is a force.

8 Contact and Noncontact Forces A contact force is exerted only when two objects are touching. A noncontact force is exerted when two objects are not touching. Magnets exert a noncontact force on each other.

9 Force is a Vector Vectors have magnitude and direction. Force has a direction and a magnitude. Force is measured in Newtons.

10 Combining Forces When more than one force acts on an object, the forces combine. The combination of all the forces acting on an object is called the net force.

11 Combining Forces in the Same Direction Forces are vectors and require a reference direction. When forces in the same direction combine, the net force is in the same direction and the size of the force is the sum of the forces.

12 Combining Forces in the Same Direction (cont.) If two people push the dresser to the right, the forces are added together.

13 Combining Forces in Opposite Directions When forces in opposite directions combine, the net force is in the direction of the larger force. The size of the net force is the difference between the two forces.

14 Combining Forces in Opposite Directions (cont.) Two people exerting a force in opposite directions show how vectors combine to create net force.

15 Challenge on your notes draw the following and answer: What is the NET FORCE on the dresser? INCLUDE direction! Draw the relative size of the net force

16 Unbalanced and Balanced Forces If the net force on an object is not zero, it is an unbalanced force. If the net force on an object does equal zero, it is a balanced force.

17 Balanced Forces

18 Balanced Forces and Motion If two people push with the same force, the door does not move. The forces have the same magnitude. The forces are in opposite directions. The net force on the door is zero and the forces are balanced. The motion of the door does not change.

19 Unbalanced Forces and Motion Unbalanced forces change motion. If two people push with different force, the door moves. The forces have a different magnitude and are in opposite directions. The net force on the door is not zero and the forces are unbalanced. The door moves in the direction of the larger force.

20 Sir Issac Newton

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22 HIS LAWS!!

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24 Newton s First Law of Motion If the net force on an object is zero, the velocity of the object does not change. If the net force is zero and the object is at rest, it remains at rest. If the net force is zero and the object is moving, it continues to move in a straight line with constant speed. Newton s Laws of Motion

25 Inertia and Mass Mass is the amount of matter in an object. The more mass an object has, the more inertia it has and the harder it is to change its motion. A bicycle is easier to push than a car because it has less mass.

26 2.1 Combining Forces Which of the following changes occur when an unbalanced force acts on an object? A motion B mass C inertia D weight

27 2.1 Combining Forces What is the net force acting on a door if one person pushes to the right with a force of 2000 N and a second person pushes with a force of 1500 N to the right? A 3500 N to the right B 3500 N to the left C 500 N to the left D 500 N to the right

28 2.1 Combining Forces You are riding a bike. In which of the following situations are the forces acting on the bike balanced? A You pedal to speed up. B You turn at constant speed. C You coast to slow down. D You pedal at constant speed.

29 Materials Needed Today Please take these materials out of your binder and place your binder under your seat or desk. Pen or Pencil Science spiral notebook Bell work sheet Bell Work Answer the following question on your bell work worksheet What is Mass? Is there a difference between Mass and Weight. Which one will be the same in space and which one won t?

30 Materials Needed Today Please take these materials out of your binder and place your binder under your seat or desk. Pen or Pencil Science spiral notebook Bell work sheet Lab Comparing Mass and Weight Bell Work 10/20 Answer the following question on your bell work worksheet Graph for the first five minutes follow instructions on lab handout #1 under Analyze and Conclude section (pg 10)

31 What is A Force and what does it include? A contact force? A balanced force? An Unbalanced Force? Who is Newton? What was his first law? What is inertia (hint use the word mass )

32 WRITE in notebook For a line graph, the equation is y=mx+b M=slope of the line (Rise/Run) B=where the line crosses the y axis When b is 0 we can calculate y by multiplying the x value with m (the slope)

33 Hints for today Slope = rise/run = (Change in y)/(change in x) #3 Ratio=weight/mass Infer=take a shot at explaining DON T Do #4 Only do numbers 1-7 and 8 is extra credit. Y=mx+b

34 Materials Needed Today Please take these materials out of your binder and place your binder under your seat or desk. Pen or Pencil Science spiral notebook Bell work sheet Bell Work 10/20 Answer the following question on your bell work worksheet Forces that are equal in size but opposite in direction are forces. If there wasn t gravity, what would happen to a ball if you threw it straight up? Solve for the net force: F=20N F=5N