Motion Detective - B

Page ______MOTION DETECTIVE - B When you construct your vehicle, it will have to travel a given distance. You have learned how to describe motion using time and distance. But, knowing about time and distance is not enough. More information is needed to truly understand how your vehicle will move. In this investigation you will use the Vernier LabPro and LoggerPro software to further investigate the idea of motion. Objective: Students will analyze data using time, distance, and velocity in order to describe constant motion. Materials Computer Vernier Interface Logger Pro Vernier Motion Detector Masking tape Meter stick Day 2: Velocity

When you want to get somewhere in a hurry, you go as fast as you can. You move at high speed. Speed tells you how long it will take to go a certain distance. To calculate speed, you know you must divide distance by time. There is another factor involved when discussing speed and that is velocity. Velocity tells two things about an object. First, it tells how fast the object is moving. This is its speed. Second, it tells the direction the object is moving. In Figure 1, when the ball is at point A, its velocity is 20 meters per second upward. When the ball is at point B, its velocity is 20 meters per second downward.

A Activity 1 Figure 1

Activity 2 B Thinking about a ball moving upward and downward is easy. But we are not going to be playing baseball. We are constructing a vehicle that must move in a given direction for a specific distance. Look at the following phrase: 25 km/hr westward. What is the speed of this object’s motion? _____ What is the direction of this object’s motion? ______You would say the speed is twenty-five kilometers per hour and the direction is westward. Velocity has a speed and a direction.

1. Why is the phrase 25 km/hr westward a velocity? Use information from the reading to support your answer. ______2. Suppose you are traveling east to visit a friend and you hear on the radio that a storm is moving 35 km/hr in a westerly direction. Should you find a place to pull over and wait for the storm to pass if the storm is in front of you? Explain your answer using information from the reading. ______Activity 3 Now that you understand what velocity is, let’s see how it works! 1. Put a piece of masking tape down on your table as a starting point. 2. Get your stop watch ready. 3. Twist the toy 4 times and hold while you wait for the timer. 4. Place him on the start line and begin recording time. 5. Turn the timer off when he stops. 6. Measure that distance. 7. Calculate speed. S = d / t It’s speed was______.

Now that you have speed you can calculate velocity. This time you are going to record direction and time. 8. Get your toy in place and wind it 4 times, holding it while you wait for the timer. 9. When he stops make a mark and then wind him up 3 times in the opposite direction. KEEP RECORDING TIME THE WHOLE TIME. 10. When he stops, stop the timer. 11. Now record the distance he went in one direction and then the other. 12. Now we can record and graph velocity.

Start 1st direction Stop 2nd start 2nd direction Second stop time distance distance distance distance North, South North, South 0 cm Left, Right 0 cm Left, Right Forward, Backward Forward, Backward Up, Down Up, Down

Graph 1

What is happening in this graph? 3. At what distance did this object start? ______how long was it at this distance? 4. Decide what direction the positive numbers will be. ______Now what direction are the negative? ______. 5. How far did they move at 1 second ______, and in what direction? 6. Finally they reached 0.2 meters, how long were they there? ______7. Describe what motion you would need to match Graph 1. Would you need constant velocity or an increase in velocity or nothing at all? ______

Analysis 1. What two things does velocity tell us about an object’s motion? a. ______b. ______

2. Describe the motion needed to make Graph 3 if it is a position vs. time graph. Use information from the investigation to support your answer. a. ______Graph 3 Position vs. Time

______) m (

n o b. ______i t i s

______o P B c. ______C A 3. What would constant motion look like on a distance vs. time graph? Sketch it below. Time