How To Calculate The Force Of Motion

Transcription

1 Force and Motion Notes

2 NEW UNIT! STEPS: 1. TURN TO THE NEXT CLEAN PAGE IN YOUR JOURNAL 2. G LUE THE TITLE PAGE A ND THE A NTICIPATION GUIDE IN 3. COMPLETE THE ANTICIPATION GUIDE. 4. BE READY TO TAKE NOTES

3 Questions to discuss: How do forces affect the motion of an object? How do the laws of motion apply to every day life?

4 Unit 5 Force and Motion Learning Goals (TEKS): Force, motion, and energy. The student knows that there is a relationship between force, motion, and energy. The student is expected to: 8.6B differentiate between speed, velocity, and acceleration 8.6A demonstrate and calculate how unbalanced forces change the speed or direction of an object s motion 8.6C investigate and describe applications of Newton s law of inertia, law of force and acceleration, and law of actionreaction such as in vehicle restraints, sports activities, amusement park rides, Earth s tectonic activities, and rocket launches

5 Sir Isaac Newton ( ) One of the world s greatest scientists Developed the 3 Laws of Motion

6 What is a Force? A force is a push or pull When one object pushes or pulls another object, the first object is exerting a force on the second object Forces are described by strength and direction And are drawn with arrows

7 Forces are measured in Newtons SI unit of force Symbol: N Measured by using a spring scale

8 There are two types of forces Balanced Forces (No change in motion) No Acceleration! Unbalanced Forces (Change in Motion) Acceleration!

9 Net Force We calculate forces using net force. The overall force on an object after all the forces acting on it are added is called the net force. Net Force = 3N

10 Balanced Forces and Motion Are equal forces acting on one object in opposite directions. Equal forces acting on an object will not change the object s motion. The net force is 0 (zero). Net force = 0 (push) Net force = 0 (pull)

11 Balanced Forces There is no change in motion

12 Unbalanced Forces and Motion Can cause an object to: start moving stop moving change direction or speed. When two forces act in the same direction, they add together. When forces act in opposite directions you subtract the forces. If one force is greater than the other force, the overall force is in the direction of the greater force.

13 Unbalanced Forces The forces acting on an object are not equal When a net force greater than 0 acts on an object the forces are UNBALANCED. One or more force is stronger than others Change in Motion occurs

14 How to calculate net force Once again - the net force is the overall force or total amount of force acting on an object (a combination of the magnitude and direction) For example, in this tug of war, the net force is 3N to the left 5N 2N The forces are in opposite directions. Subtract the numbers.

15 More examples of net force calculations Two people are trying to push away a box full of rotting eggs, who ends up with the box? Sam 10N Omar 15N If there are two people trying to get this box full of money, who ends up with it? Lauren 20N Olivia 30N

16 Calculation Practice Unbalanced 225 N Unbalanced 13 N Bill Nye Balanced 0 N =

17 Calculating Force Force = mass x acceleration Don t forget the units!

18 Let s examine the Spring Scale more closely Definition: A spring scale is a tool used to measure force. It works in the same way the rubber band does. The spring inside it stretches based on the amount of force added to it. Use will use a spring scale in the lab today

19 Simple Machines and Forces Inclined Plane Screw Wedge Lever Pulley Wheel and Axle

20 So what is a simple machine and what makes them so simple? A simple machine has few or no moving parts. They often use only the force (effort) of a person to do the work. Simple machines make our effort easier.

21 Why are they so important?? Simple machines are important because they can make a physical job easier by changing the magnitude (amount of work) or the direction of the force exerted to do work. The amount of force output is greater than the size of the force you put in.

22 Why Use Simple Machines? For the mechanical advantage Making something easier to do, but it takes a little longer to do it For example, going up a longer flight of stairs instead of going straight up a ladder

23 Force and Motion Lab EXPLORATORY STATIONS

24 Journal In table of contents Forces Lab On the next clean page, write for the title Forces Lab

25 Lab explanation and expectations This is a rotating station lab You will be timed. When the timer goes off, move to the next station in numerical order. For example, if you start at Station 2, your next rotation is to Station 3. If you are not following expectations for labs, I will have you sit out Use the spring scales and all supplies appropriately

26 In your Journal: Write down stations 1-6 leaving room to answer 2-4 questions for each station you may need 2 pages Station1 Station 2 Station 3 Station 4

27 Station 1 - Ball 1. Place the ball on the counter, where the X is. 2. Write in your journal: Is this an example of balanced or unbalanced force? Why? 3. GENTLY bounce the ball so that it bounces up from the floor to your hand. 4. Draw the movement in your journal and label the direction of forces. 5. Write in your journal: Is this movement an example of balanced or unbalanced force? Why?

28 Station 2 - Dominoes 1. Set up the dominoes in a row so that they will touch each other when they fall. 2. Write in your journal: What type of force is going to make the dominoes fall? 3. Knock the dominoes over. 4. Draw your domino set up in your journal and draw arrows to show the direction of movement.

29 Station 3 Velcro Paddle and Ball With a lab partner: play catch 2 or 3 times. Write in your journal answers to these: 1. What is the force that makes the ball stop? 2. Is there a different force making the ball fall towards the ground? What is it called? 3. When the paddle stops the ball, is that force moving in the same direction as the ball?

30 Station 4 Spring Scale One person holds the spring scale while another person puts weights on the scale. Write these down in your journal: 1. What does the spring scale measure? 2. Write down the Force in Newtons (N) for each weight. Weight: g g g Force (N):

31 Station 5 Force Problems Work these problems 1. Draw the boxes and arrows, including the forces in Newtons. 2. Show your math work!

32 Station 6 Tug of War! View the picture and then sketch it in your journal: Tabitha Zach Tabitha and Zach are playing tug-of-war. If Zach pulls the rope to the right with a force of 800N and Tabitha pulls the rope to the left with a force of 800N, what will happen to the flag in the middle of the rope? Write this sentence and fill in the blanks: The flag will because.