Lecture # 21 SCIENCE 1 ASSOCIATE DEGREE IN EDUCATION Measuring motion

Speed and Velocity Many Students might already know that when the model car is travelling, the expression for relating distance and time is: speed = distance/time. But a distinction needs to be made between the speed of an object and its velocity. Speed refers to a quantity; velocity refers to a quantity and direction. When specifying velocity, you also need to indicate the direction the object is moving.

Weekly Plan This week, Students deepen their understanding of force and motion. They spend time measuring and graphing the speed of their model car at specific points in time. In addition to collecting data about the movement of their model car, they also practice graphing the data. As a visualization of data, a graph allows you to quickly determine if the car is: 1.travelling at a steady rate 2.moving at different speeds 3.changing speeds over a given distance.

Experimenting with speed and momentum Tell Students that this week they will investigate motion. They will do so by obtaining quantitative data about the speed of their model car at various points in time. Hand out yardsticks (or measuring tape) and a stopwatch (or a watch that shows seconds) to each group. Tell them to work with the knowledge about forces from last week and design a scenario in which: 1.their model car moves the longest distance 2.their model car reaches the highest speed.

Students should have the same experience and should focus more on the relatively difficult concept of gravity. To do so, have all groups work with their cars going down ramps instead of using other propulsion mechanisms that are harder to quantify (such as a push with a hand or the tension of rubber bands). They can build simple ramps using a piece of plywood and some bricks or books. For better incline comparison, bricks of the same height will work better than different books. Experimenting with speed and momentum

Use the entire session for Students to design and experiment. Circulate among them while questioning them. Ask for their ideas on how to set the class record with their car. Then ask why they think that strategy would work best using their knowledge of balanced and unbalanced forces. Listen carefully for any misconceptions about motion. Instead of just correcting any wrong answers, ask probing questions. These questions will allow the them to grow in their thinking and find the correct answers in their group. Experimenting with speed and momentum

Once a group has a promising hypothesis and design, ask the group members to also think about how they will measure and record their data. While they conduct their experiment and record their data, encourage them to constantly refine their approach. They may even revise how they collect the data to make the most compelling case. Make sure that they discuss what might cause changes in the data and have them explain those changes. This is a good opportunity for Student Teachers to carry out an experiment on their own. They should test their hypothesis by changing a variable at a time to watch for the expected effect. Work with them on fine-tuning their ability to design and carry out controlled experiments. Again, guide them through questioning rather than correcting their responses. Experimenting with speed and momentum

Make sure that at the end of this session, each group has data for distance and speed. Have them explain all the forces acting on the car at the start, when it is in motion, and when it comes to a standstill. Experimenting with speed and momentum

To facilitate their investigation, you might ask the following questions: 1.What makes the car move (down the ramp)? 2.What keeps it from moving faster/farther? 3.What are the effects of the different forces on the car (friction, gravity, etc.)? 4.What does increasing or decreasing the angle of the ramp do to the motion of the car? Experimenting with speed and momentum

Determine if the model cars can run for several seconds and cover a longer distance. Then ask Students when they think the car reaches its highest speed and how they can prove it with their data. In order for them to answer this question, they need to measure the speed at various points so that they can compare the different intervals. This is valuable additional learning and skill building. It provides an opportunity for an additional discussion about maximum speed and average speed of the car Experimenting with speed and momentum