Calculating Average Speed and Comparing Kinetic and Potential Energy Author: Matthew Kurth Grade Level: pre-ap 6 th grade Science (45 minute class) Sources: CPO Science (Force and Motion) o Curriculum Resource Guide: Car and Ramp, Section A-3 (some of the activity packet is from this source) Texas Essential Knowledge and Skills: Concepts: 6.8 Force, motion, and energy. The student knows force and motion are related to potential and kinetic energy. The student is expected to: (A) compare and contrast potential and kinetic energy; (C) calculate average speed using distance and time measurements; 6.2 Scientific investigation and reasoning. The student uses scientific inquiry methods during laboratory and field investigations. The student is expected to: (C) collect and record data using the International System of Units (SI) and qualitative means such as labeled drawings, writing, and graphic organizers; (D) construct tables and graphs, using repeated trials and means, to organize data and identify patterns; In this lesson the students complete an activity where average speeds are calculated from multiple trials that they do. Photogates will gather times of a car rolling down a ramp, and the students will use the formula of distance over time to calculate the average speeds. Kinetic and Potential energy will also be covered. Students will compare and contrast Kinetic and Potential energy in different situations. It is important for students to understand these concepts, so they can understand and describe the motion that they observe. 2010 The University of Texas at Dallas
Performance Objectives: Students should be able to State the formula to calculate average speed. Calculate the average speed of an object and give its units when given the distance it traveled over the amount of time it took. Decide if Kinetic or Potential Energy is greater for an object and if they are increasing or decreasing. Appropriateness of Lesson to the Grade Level: Hands on experience and student collaboration will help the students better understand speed, Kinetic energy, and potential energy. Having defined roles will also help the students stay on task and work together as a group. Materials List: Materials for a group of 4: 1 straight physics ramp 1 Physics stand 1 car 2 photogates with input cords for each 1 CPO timer with outlet near it to plug it in Materials for each student: Activity packet calculator Advanced Preparations: Have the ramps already connected to the physics stands at the fourth or fifth hole from the bottom. Have a car already on each ramp Have both photogates attached to each ramp and input into the CPO timer (the photogate higher on the ramp goes into input A and the other into input B). Have a ramp set up at the front of the class so the students can see when you demonstrate the activity. Safety: There are no major safety concerns for this lesson. Page 2 of 10
ENGAGEMENT What the Teacher Will Do As students enter the classroom have them pick up a warm-up. Have the students complete their warm-up independently and pick them up after they are finished. Play video from you-tube of Olympic skier going down ramp and being projected out and down from the end of the ramp. Have a discussion with the class over what they put on the warmup. Discuss how to calculate average speed Probing/Eliciting Questions How would you describe this skier s motion? What term can we use to describe how fast he is going? What energy terms can we use to describe the skier? What is the formula for average speed? When does an object have Kinetic energy? When does an object have potential Energy? What is an example of a decrease in potential energy? Time: 10_ Minutes Student Responses and Misconceptions -He is going really fast. -speed -high energy Kinetic Energy -they might not include potential energy because of the speed of the skier. Time over distance When it is moving correct When it is held not necessarily it depends on the objects height off the ground Page 3 of 10
EXPLORATION What the Teacher Will Do Have the students move to the lab tables in their predetermined groups of 4 with ramps already set up. Assign roles for each member of the group. Assign a driver, catcher, timer, and mover ; these roles responsibilities are described in the activity packet. Pass out an activity packet (attached to end of this lesson) to each student for them to fill out. Demonstrate the activity to them. Stress that the car s wing must be just above the photogate before releasing it. Explain that they will have 3 trials recording the time before moving the photogate lower. The times will be averaged and times will be gathered from 3 distances. Have the class practice calculating an average on their calculators with you. Have the class begin on the packet. Walk around the class making sure that they understand the activity and are staying on task. Ask questions throughout the activity to see if they understand what is taking place After the groups have finished the packet, have the students turn off the timers and return to their seats. Probing/Eliciting Questions -Before the car is released does it have Potential and/or Kinetic energy? -When it moves down the ramp is the Kinetic energy increasing or decreasinghow about potential energy? -Should the average speeds change as the distances on the ramps change? Why? Time: 20 Minutes Student Responses and Misconceptions No, it has neither because it is not moving. It has no potential energy when it is moving only kinetic energy. No, they should stay the same because the times are increasing too. Page 4 of 10
EXPLANATION What the Teacher Will Do Have a discussion on how they calculated the average speed. Have a discussion over the change in potential and Kinetic energy. Time: 5 Minutes Probing/Eliciting Student Responses Questions and Misconceptions How do you calculate the average speed of an object? How do you get the units for the speed? It s always miles per hour What process do you use to figure out the units you will use? Before the car is released down the ramp does it have kinetic energy and/or Potential energy? No energy because it is At the bottom does the car being held. have potential and/or Kinetic energy correct Kinetic energy? Kinetic energy increases and Which increases and which the potential energy decreases as the car rolls disappear after it begins to down the ramp? move. If you were given the Maybe Kinetic energy of an object One goes up when the other could you calculate the goes down potential energy? What kind of relationship does potential and kinetic energy have? ELABORATION What the Teacher Will Do Have a discussion with the class over speed in real life. Disuses with the class which units to use in a situation. Time: 5 Minutes Probing/Eliciting Student Responses Questions and Misconceptions When do we use speed to describe motion? What objects do we describe by speed when we talk about Cars, planes, baseballs, them? tennis serves, skiers If you knew your flight from Dallas to Houston lasted 1 hour and Houston is 240 miles away, could you calculate the average speed Page 5 of 10
Have a discussion over potential and kinetic energy by having the class describe the motion of a person riding a swing. Place a picture on the overhead that shows a person on a swing at different points. Have them point out the highest potential and Kinetic energy, the lowest kinetic and potential energy, and increasing/decreasing potential and kinetic energy. you were moving on the trip? What process do you use to figure out the units of an average speed? What would the units be of the average speed of a bird that flew 5 wing lengths in one second? Where is the highest Kinetic energy?-potential? Where are Kinetic/potential energy increasing/decreasing? -The highest Kinetic energy is at the farthest point of the swing forward The Kinetic energy increases from the far back of the swing to the front of the swing. EVALUATION What the Teacher Will Do Pass out the Evaluations to each student and have them fill it out individually. Evaluations are attached at the end of this lesson. Pick up the evaluations when they are done. Probing/Eliciting Questions Time: 5 Minutes Student Responses and Misconceptions Page 6 of 10
Warm Up 1) What is the equation for average speed? 2) A plane flew 350 kilometers in 30 minutes, calculate the average speed and include its units. If I was holding a tennis ball at shoulder level and dropped it, so it fell towards the ground 3) While it was falling was the Kinetic energy increasing or decreasing? 4) Before I released the ball was the Kinetic or Potential energy greater? Page 7 of 10
(Activity Packet) Describing speed What information do you need to describe your speed? To describe your speed, you need two things: 1. The distance you traveled, and 2. The time it took you to travel that distance Practice calculating average speeds by filling out the table below. Make sure that each speed has units with it (ex: meters / hour).you may use a calculator. Example Distance Time Speed 100 meters 10 seconds 50 miles 1 hour 10 feet 15 seconds Page 8 of 10
Average Speed Experiment 1. Make sure the photogate connected to input A is placed near the top of the ramp with enough room for the car s wing to be above the photogate s sensor. 2. Place the other photogate at a distance of 20 cm from the first photogate, making sure that this photogate is connected to input B on the Timer. 3. Make sure the Timer is plugged in and turn it on using the switch on the left side. Adjust timer to measure interval by pushing the bottom yellow button until the green light indicating interval is lit up. Then make sure photogates A and B are activated (push yellow buttons above A and B on timer, to light up green light) 4. With car as close to the top of the ramp as possible, have the driver release it so it runs to the end of the track where the catcher can stop it. Make The timer makes sure a time was recorded. If it was, this should be the amount of time it took for the car to travel between the photogates. Record this time in Data Table 1, under Time 1 for 20 cm. The timer then resets the timing device by pressing reset. 5. Repeat this measurement two more times, recording them as time 2 and time 3. Calculate the average time and record. (add the three times and divide by 3) 6. The mover moves the lower photogate down the ramp, 40 cm from the top photogate. Repeat steps 4 and 5, except recording times on the 40 cm row. 7. The mover moves the lower photogate down the ramp, 60 cm from the top photogate. Repeat steps 4 and 5, except recording times on the 60 cm row. Page 9 of 10
Data Table 1 Position-Times Position of Car Time 1 Time 2 Time 3 Average time 20 cm 40 cm 60 cm Evaluation 1) What is the formula for average speed? 2) Calculate the average speeds and include its units. A camel walked 20 km in 10 hours 3) On a rollercoaster a cart is resting at the top of a hill, is the Kinetic energy or Potential energy greater? 4) As the cart rolls down the hill, is the Potential energy increasing or decreasing? Page 10 of 10