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Force and Motion Weekly Highlander Sheet Students will brainstorm about “force” and create a working definition for force. Students will investigate to discover and identify evidence and various types of forces. Warm Up: FORCE We have all heard the word “force”- we have even used it… but can you define it? 1. Write out your own definition of force. 2. What would a scientific definition of force sound like? 3. Are there any forces acting on you right now? Nature of Forces Forces are a push or pull Forces can be added Forces have direction as well as size Unbalanced forces result in a change in motion Balanced forces result in no change in motion Evidence of Force For each item in the basket: 1. Indicate what force is present 2. Describe the force. 3. Identify what EVIDENCE you have that there are forces acting. What should I know now? … Unbalanced forces cause change in motion. Forces are a push or a pull. Types of forces Magnetic (non-contact) Gravity (non-contact) Elastic Spring Friction (contact) Electrostatic (non-contact) Cetripedal Types of forces Magnetic (non-contact) Gravity (non-contact) Elastic Spring Friction (contact) Electrostatic (non-contact) Cetripedal Exit Ticket: What is evidence that there are unbalanced forces acting? Force and Motion Warm Up: Net force defined… The additive force acting on an object Individual practice… write these in your journal for notes Let’s practice… Elbow partners take good notes Acceleration Defined… A change in velocity's speed or direction http://www.youtube.com/watch?v=dQmYBF_Sd8I Lets try a problem… Force and Motion HT TPS://WWW.YOUTUBE.COM/WATCH?X -YTTS=1422503916&X -YTCL=85027636&V=CGNBIBVYL2W Warm Up: F=ma Lets try a problem… Solve this problem using G.U.E.S.S. method F= ma word problems 1. If a ball with a mass of .30 kg is hit by a bat with a force of 50 N, what acceleration will be given to the ball? 2. What force is needed to accelerate a car with a mass of 950 kg at a rate of 5.0 m/s2? F= ma story problem Your little brother wants you to push him across the ice rink. He has a mass of 20kg. Frictional forces are small, only 2 N. How much force do you need to exert to give him an acceleration of 3.0 m/s2. Hints for Problem-Solving Read the problem carefully at least once Draw a picture of the system, identify the object of primary interest, and indicate forces with arrows Label each force in the picture in a way that will bring to mind what physical quantity the label stands for (e.g., T for tension) Draw a free-body diagram of the object of interest, based on the labeled picture. If additional objects are involved, draw separate free-body diagram for them Choose a convenient coordinate system for each object Apply Newton’s second law. The x- and y-components of Newton second law should be taken from the vector equation and written individually. This often results in two equations and two unknowns Solve for the desired unknown quantity, and substitute the numbers Fnet, x max Fnet, y may Whiteboard and Teach Diagnoser: Identifying Forces Diagnoser: Effects of Pushes and Pulls Set 1 Decide who will be the initial SCRIBE, take turns Everyone must say something during the presentation portion Complete the following as a team: 1. Read the question 2. Reread the question 3. Rule out the incorrect answers by determining what the outcome of would be 4. Finally write a statement and DRAW a picture that shows the concepts on the correct answer. Example Gravity pulls with equal down force as the table pushes with up force After a lecture on forces in science class, Frank was thinking about the forces acting on a box at rest on his desk. Which statement do you think best represents the forces acting on the box? (a) No forces act on the box at rest. (b) The force of gravity is acting on the box. Resulting in NO NET FORCE- so the the only book staysforce put (c) Earth pulls down and the table pushes up equally on the box. (d) The downward pull of gravity is larger than the upward push of the desk. Force and Motion Warm Up: Choose the best answer Frank pushes a box at rest, then pushes harder on the box until it starts to move. Frank pushes it across the desk at a constant speed. Which of the following statements best represents the forces on the box now? (a) The table can only push up on the box so any sideways force will cause it to move. (b) table. The downward force of gravity is still larger than the up push of the (c) The box will continue to move until the force of motion from Frank is used up. (d) The box moves because the table can not push to keep the box from moving. (e) The horizontal friction is exactly equal and opposite to the push from Frank. Friday Quiz Take it Correct it Force and Motion Warm Up: Can you solve this math problem? Use the Pythagorean Theorem a2 +b2 = c2 How does this apply to Physics? Distance, Displacement, Frame of Reference Distance: the actual footpath Displacement: How far from the frame of reference. Frame of Reference: Location used to locate or measure movement of a point in space. How far from the start is Anna? In the Vector Addition Lab, Anna starts at the classroom door and walks: 2.0 meters, West 12.0 meters, North 31.0 meters, West 8.0 meters, South 3.0 meters, East What is Anna’s distance? What is her displacement? How far from the start is Anna? WORK THIS PROBLEM… In a grocery store, a shopper walks 36.7 feet down an aisle. She then turns left and walks 17.0 feet straight ahead. Finally, she turns right and walks 8.2 feet to a final destination. (a) Determine the magnitude of the overall displacement. Optional (b) Determine the direction of the displacement vector relative to the original line of motion A student drives his car 6.0 km, North before making a right hand turn and driving 6.0 km to the East. Finally, the student makes a left hand turn and travels another 2.0 km to the north. What is the magnitude of the overall displacement of the student? Vector quantityMagnitude and direction Mac and Tosh are doing the Vector Walk Lab. Starting at the door of their physics classroom, they walk 2.0 meters, south. They make a right hand turn and walk 16.0 meters, west. They turn right again and walk 24.0 meters, north. They then turn left and walk 36.0 meters, west. What is the magnitude of their overall displacement? Vector quantityMagnitude and direction Force and Motion Warm Up: At what velocity is the stick-guy inside the train moving? What is your frame of reference? SWBAT/ Objective: 1. Students will use frame of reference in order to determine position. 2. Change in position will be used to calculate velocity. Frame of Reference 1. What is a frame of reference? system for specifying the precise location of objects in space and time http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=140 2. How is it used to measure motion? 46 Notation Change in position This symbol is used to indicate the starting position of an object. “i” stands for initial. This symbol is used to indicate the end position of an object. “f” stands for final. This symbol is used to indicate change in position of an object. 1. 2. 3. How fast? Calculating Velocity Velocity is a speed in a given direction. Velocity is calculated using a change in position during a certain amount of time. ______________ = V (in a given direction) Time https://www.youtube.com/watch?v=DRb5PSxJerM Complete this assignment Due by the end of the period Force and Motion Is displacement more like the length of a rope that is pulled tight or the length of a coiled rope? It is more like the rope that is pulled tight because it measures the shortest distance between two points. 52 Distance The length of the path between 2 points. 0……………………………….1 mile Total distance? 1 mile Total displacement? 1 mile 53 Displacement Is the direction from the starting point and the length of a straight line from the starting point to the ending point. 0………………………………………….1 mile Total distance: 2 miles Total displacement zero 54 How are displacements combined? Displacements are combined using vector addition. We added the 2 vectors for the car to calculate its total displacement: The car went 1 mile to the right Then back one mile For a total displacement of zero 1 -1 0 55 SWBAT/Objective: By the end of the period each student will accurately and confidently describe a position over time graph. Set Up the Axes~ 1. Make x & y axes on a white board 2. Label (y) South, label (–y) North 3. Begin y axis at the far left almost to end of the right side of the whiteboard. 4. The X axis will be Time without units, and the Y axis North/South without units. S Time N Jobs: Marker Person 1. One person acts a marker person… you sit facing South with marker in hand. 2. Your job is to move the marker north or south at the same rate as Ms. Lin moves north or south, -also to stop/pause when I do. 3. DO NOT move the marker left or right 4. At the start the marker is place a zero time wherever the teacher is standing on the north south line. Jobs: Time Puller 1. Another person is the “Time Puller”: This person stands at the – East side of the table (left as facing North) 2. Place the white board at arm’s length toward the middle of the table, with just finger tips on it to get ready to pull toward them. 3. When the graphing time starts- the Time Puller pulls board toward them. 4. As the teacher counts down and begins to move the time puller slowly pulls the whiteboard toward them (east) at steady rate. 5. DO NOT stop or slow down or speed up. Let’s DO some graphing! I will call out what I am doing at each step. Force and Motion Warm Up: What is the motion shown in this graph? Position-Time graphs with Displacement • The distance traveled by an object in a period of time often is expressed using a line graph. A line graph visually conveys info using sets of data Directions: 1. Make a graph, use graph paper. Label X-axis, Time (s) and Y-axis, Position (m) 2. Mark the following data points: (0,0), (2,40), (4, 80), (6,120), (8,160), and (10, 200) 3. With a straight edge, connect the points 4. Describe the motion shown on the graph 5. What’s the distance traveled? Displacement? 6. Calculate the velocity. 63 Motion Graph • Draw a graph (on graph paper) • Label X-axis time (s) & Y-axis position (m) • Graph the following coordinates – (0,5), (5,10), (15,10), (20,10), (25, 25), (30,15) Questions 1) Describe the motion 2) Find the velocity between 0-5s and 15-20s 3) What’s the distance traveled? 4) What’s the displacement? 5) Between what times was the motion the fastest? 64 Force and Motion Warm Up: Total distance? Displacement? Start 2 miles 2 miles End 1 mile 2 miles What 2 properties does a vector quantity have? 1. 2. ? __/16 Friday Quiz Key 1. Name 2 properties a force has: ◦ Size 1pt ◦ Direction 1pt 2. Distance: 7 miles 1pt ◦ Displacement: 0 miles 1pt 3. Xi 1pt Xf 1pt Δx=16 cm How fast? 0.8cm/min 4. B 2pt 5. C 2pt (1pt number, 1pt units, 1pt direction) (1pt number, 1pt units, 1 pt direction) Force and Motion Warm Up: Ms. Lin lives across the street from HHS on Hoquiam, right near the Tennis Courts. Her home is roughly 1400m away from the main entrance. She forgot her Graded Quests from last week and needs to run home to grab them before 1st period. Starting at the main school entrance on Hoquiam, she runs to the crosswalk, waits for many cars to pass, then walks across the street, walks one block, waits for a car to pass at the next block, then walks into her house. She runs the whole way back, but has to wait at the crosswalk again. What would the graph of Ms. Lin’s motion look like? Todays SWBAT/Objective: Use data, graph, and words to identify and analyze motion of an object. Homework Due Wednesday! There are 6 problems… this slide shows only the first problem. Create the following table in your journal. 1. In pairs you must match the correct story, graph, and data set. There is one bogus set. Use the table above to help stay organized. 2. When you think you have the correct answer- get Ms. Lin to verify. 3. Last- sketch the graph and relate it back to the data and story in your journal. Force and Motion Warm Up: What is slope? Position: Time Velocity: Time Remember last week… Let’s look at velocity. Can we graph it? Velocity is the change in position(in a given direction) over time Velocity Definition : Velocity is the displacement (in a given direction) in a unit of time. Mathematically : velocity = displacement / time ( in a direction) Rate and direction of motion: 30 m/s south; 300m/s up * If motion is in one direction, speed and the rate of velocity are the same. * In taking data from data tables and graphs, note the start position— motion does not always start from position 0. Be sure to look at the number on the y axis. *Velocity in a position :time graph is the slope of the line. Units: m/s, km/hr, km/s, mm/day, etc. ALWAYS GIVE A DIRECTION Do not use mps. Can you find the match? Force and Motion Warm Up: You can do this … Calculating Velocity 1. The miners in Chile were 624 m underground. It took 15 minutes to bring up the first miner to be rescued. What was the average speed of the rescue capsule? 2. The International Space Station has an orbital speed of about 8800m/s and orbits the earth about every 90 minutes. How big is the orbit? Complete this assignment Position VS time Position (m) 35 30 25 20 Position (m) 15 10 35 5 30 0 1 2 3 4 Position (m) 5 6 7 25 20 15 10 5 0 1 2 3 4 5 6 7 Copy these two tables to your journal Velocity Velocity ---- ---- -15 5 -10 5 -5 5 0 5 5 5 10 5 Velocity vs Time Chart Title 15 y = 5x - 20 R² = 1 10 5 0 1 2 3 4 -5 -10 -15 -20 Velocity (m/s) Velocity (m/s) 5 6 Complete this assignment Force and Motion Force and Motion Instantaneous or average? https://www.youtube.com/watch?v=pfTTHx9kCHk Force and Motion Physics Exam Force and Motion Read and report1.What is the article about? Identify the central idea. 2.Why do you think its about that? Support the central idea with evidence. 3.What do you think it means? Be sure that your analysis tightly connects evidence to central idea. Force and Motion Warm Up A halfback (m = 60 kg), a tight end (m = 90 kg), and a lineman (m = 120 kg) are running down the football field. Consider their ticker tape patterns below. Compare the velocities of these three players. How many times greater are the velocity of the halfback and the velocity of the tight end than the velocity of the lineman? Dimensional Analysis How do I figure out how much…? How much force do I exert on the floorand inevitably the Earth? Weight = 124 lbs Step 1 Step 2 124lbs 1N .225lb Step 3 = 1lb = 4.45 N 1N = .225 lb 1kg = 2.20 lb 1lb = .454kg X what is in same line …then ÷ Dimensional Analysis How do I figure out how much…? What is the mass of a 40 N cat? Step 1 40N Step 2 .225lb Step 2 1N 1lb = 4.45 N 1N = .225 lb 1kg = 2.20 lb 1lb = .454kg Step 3 Step 4 X what is on top .454kg = ÷ what is on bottom Step 3 1lb Dimensional Analysis How much force do I exert on the floorand inevitably the Earth? ….Let’s just say I weigh 124 lbs Extras 1. Ben Tooclose is being chased through the woods by a bull moose which he was attempting to photograph. The enormous mass of the bull moose is extremely intimidating. Yet, if Ben makes a zigzag pattern through the woods, he swill be able to use the large mass of the moose to his own advantage. Explain this in terms of inertia and Newton’s first law of motion. 2. You are traveling in space and are working outside of your spaceship making repairs. You accidentally throw your wrench. What happens to the wrench? Why is this different from what would happen on earth? 3. You have just been to the grocery store and have several paper bags full of groceries standing in the back of your van. You have to make a sudden stop. What happens to the groceries and why?