CH.3 COLLISIONS
FM: 3.3.1 WARM-UP Students gather evidence about the velocity change of objects in a collision. (10 min) Both Objects will Change Velocity Only 1 Object will Change Velocity Neither Object will Change Velocity
FM: 3.3.1 WARM-UP 1. What do you notice about the change in velocity on the objects? 2. Why do you think the objects in each collision experienced a different change in velocity?
Key Concept: FM: 3.3.1 WARM-UP Even though the force exerted on each object in a collision is the same strength, if the objects have different masses, their changes in velocity will be different. Remember that colliding objects experience forces of the same strength, but those forces are exerted in opposite directions. What then is the relationship between mass, force, and change in velocity?
FM 3.3.2 READING REREADING CRASH! Revisit the text to gather evidence about why equal strength forces exerted in collisions cause different changes in velocity. (20 min) To date you have investigated the strength and direction of collision forces; In a collision, how do forces affect the objects? Now you will gather evidence to answer a new question investigation question: You will revisit Crash! to look for evidence that will help explain why the same strength forces sometimes cause similar changes in speed for colliding objects, while other times, they cause different changes in speed.
FM 3.3.2 READING REREADING CRASH! Why are the effects of a collision between a bug and a car's windshield so different from the effects of a collision between two bugs? Read paragraphs 3 and 4 of Crash! and then answer the questions on the right. As you read, you may want to highlight or annotate parts of the text that could prove helpful. BEGIN READING HERE Annotate or highlight additional parts of the text
FM 3.3.2 READING REREADING CRASH! Why was the end result of a collision between two bugs so Why are the effects of a collision between a bug and a different car's windshield from a collision so different between from one the bug effects and of the a collision between two bugs? windshield? DISCUSS IDEAS WITH A PARTNER! EQUAL STRENGTH FORCE OPPOSITE DIRECTION different changes in velocity same change in velocity
FM: 3.3.3 STUDENT DISCUSSION WORD RELATIONSHIPS Students use key vocabulary to explain why the velocity changes experienced by colliding objects can be different. (15 min) You will work with a partner to create sentences about the effects of forces in a collision. Your sentences should answer the following question: Why are the effects of collisions different if the force on each object is the same strength? Jot down your ideas on scratch paper if needed! 1. Create sentences with your partner 2. Share sentences across the table 3. Be prepared to share with the class
FM: 3.3.3 STUDENT DISCUSSION WORD RELATIONSHIPS A collision will affect objects of different masses in different ways. Even though the force strength on the objects is equal, the force will have a greater effect on the velocity of the less massive object. For example, when the more massive bowling ball collided with a lighter bowling pin, the force on both objects was the same, but the pin moved much more quickly afterward because it was less massive. Even though the force exerted on each object in a collision is the same strength, if the objects have different masses, their changes in velocity will be different.
FM: 3.3.3 STUDENT DISCUSSION WORD RELATIONSHIPS Even though the force exerted on each object in a collision is the same strength, if the objects have different masses, their changes in velocity will be different. We have examined two Investigation Questions for this chapter: 1. What are the forces like in a collision? 2. In a collision, how do forces affect the objects? Can you recall your explanations for the first question and try to build on it to answer the second question? Describe the forces in a collision? They are the same size and exerted in the opposite direction. Describe how the objects in a collision change velocity. How are the objects affected? The objects change velocity depending on their mass. The same size force will make an object with less mass have a greater change in velocity.
GRAPHING Graphing changes in velocity FOLDER P.3 GRAPHING MOTION PROBLEMS Students will graph the velocity change of a vehicle and be able to determine whether the vehicle accelerated, decelerated, or traveled at a constant speed. (15 min). In our studies we have examined how forces effect the velocity of an object. - A greater force will cause a greater change in velocity. - When the same amount of force is applied to an object, the less massive object will have a greater change in velocity. - In collisions, the force being applied to both objects is always equal in strength and opposite in direction. BUT WHAT DOES THIS CHANGE IN MOTION LOOK LIKE VISUALLY. How can we graph motion to show a change in velocity (the acceleration)? What does 1. Acceleration look like on a graph 2. Deceleration look like on a graph 3. Constant speed look like on a graph
GRAPHING Graphing changes in velocity FOLDER P.3 GRAPHING MOTION PROBLEMS We know there is a difference between speed and velocity - Speed is the distance an object travels over time. - Velocity is speed in a given direction While forces are being applied to an object, the objects velocity will change. - Acceleration: Start moving, speed up - Deceleration: Stop moving, slow down
Distance (m) Speed (m/s) GRAPHING Graphing changes in velocity FOLDER P.3 GRAPHING MOTION PROBLEMS WHAT DOES ACCELERATION LOOK LIKE? On a graph of distance vs. time On a graph of speed vs. time 50 40 A curved line. 30. 20. 10.. 0 0 1 2 3 4 Time (s). 2.5 m 10 m 21 m 32 m 10 5. 8. 6 4. 2. 0 0 1 2 3 4 Time (s). A straight line 5
GRAPHING Graphing changes in velocity FOLDER P.3 GRAPHING MOTION PROBLEMS On a Velocity vs. Time Graph - Acceleration: Straight line Upward - Deceleration: Straight line downward - Constant Velocity: Straight Horizontal Line
GRAPHING Graphing changes in velocity FOLDER P.3 GRAPHING MOTION PROBLEMS Go to p.3 Graphing Motion Problems - Label the Y axis with Velocity (m/s) - Label the X axis with Time (s) - Place appropriate numbers on the Y and X axis - Complete graphs 1-6 using the descriptions above each graph. - Then indicate on each graph the following: 1. Acceleration = 1 2. Deceleration = 2 3. Constant Velocity = 3 4. Circle any point when the car stops
FORMULAS Explaining motion with math FOLDER P.4 FORMULAS CALCULATING MOTION WITH MATH Students will utilize mathematical formulas to calculate and explain motion. (15 min).
FORMULAS Explaining motion with math FOLDER P.4 FORMULAS CALCULATING MOTION WITH MATH What is the velocity of a jet plane that travels a distance of 7,200 km in 9 hr? 1. Identify Variables: V =? d = 7,200 km t = 9 hrs THE 5 STEP METHOD The same process can be utilized to calculate for acceleration or force 2. Write Formula: V = d / t 3. Substitute numbers and units V = d / t = 7,200 km / 9 hr 4. Solve for unknown variables. V = d / t = 7,200 km / 9 hr = 800 km/hr 5. Include the proper unit
FM 3.3.4 HOMEWORK Students explain why collisions between objects of unequal mass are affected differently. They also read an article about kinetic energy. Sherman Stories Help explain to Sherman why collisions between objects of unequal mass are affected differently. Read Reading Wrecking Ball! You will read, highlight, and annotate an article about kinetic energy. Read Highlight - Annotate PLACE ANSWERS HERE PLACE ANSWERS HERE