In the first four lessons of the unit, students follow Galileo’s methods to observe the speed of balls rolling uphill and downhill, and capture the motion in ‘streamer graphs’. By interpreting the graphs, they develop the concept that acceleration/deceleration is change in speed per unit time. They experiment with balls rolling up and downhill, and gather data to predict the height required for a ball to take 1 second to hit the ground, and test the prediction.

### Lesson 1: Constant Speed

The challenge in this lesson is for students to walk at a constant speed, first slowly and then faster, and discover that faster speed corresponds to travelling a greater distance in unit time. Students make ‘streamer graphs’ using paper streamers to represent the distances walked per second, using a real or virtual metronome to mark equal time intervals (seconds).

### Lesson 2: Rolling Downhill

The challenge in this lesson is for students to discover what happens to the speed of a ball when it rolls downhill. Students predict what will happen and discuss their predictions, before working in groups to create ‘streamer graphs’ using paper streamers to represent the distances the ball rolls each second.

### Lesson 3: Falling Balls

In this lesson students discover the height from which a ball needs to be released for it to take 1 second to hit the ground. Students use a variety of measuring devices to find the heights for a half second and a quarter second drop and use their results to predict and then measure the height for a 1 second drop.

### Lesson 4: Rolling Uphill

In this lesson students undertake two activities showing deceleration. First, they predict what will happen when a ball rolls uphill, then work in groups to create ‘streamer graphs’ representing the decreasing distances that the ball rolls each second. Students then investigate how far a ball rolls along a flat track with its surface altered to have more friction (covered in different ribbons), linking increased roughness with more deceleration.

### Lesson 5: Measuring Forces

The challenge in this lesson is for students to make and calibrate their own forcemeters and use them to measure pushes and pulls. Students discover what happens when two forces pull in opposite directions and draw force diagrams to represent the results.

### Lesson 6: Modelling Force and Motion

In this lesson students make a streamer graph of the motion of a car or trolley when it is being pulled by forces in opposite directions. The forces on the car are provided by masses on strings over pulleys. After discussions about the use of pulleys and forcemeter accuracy, students set up their equipment and predict what will happen. They then create streamer graphs to represent the distances the car or trolley moves each second.

### Lesson 7: Complex Motion

Students investigate the motion of a ball in two dimensions, as it travels across a sloping table. They predict the path of the ball, before tracing its path on butcher’s paper. Then they change the angle of the launcher so that the ball hits a specified target on the table. Class discussion focuses on the path of the ball and the reasons for this path, using their knowledge about the relationship between force and motion.

Last updated December 11 2018.

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