How I Teach - Keep it practical in physics

3rd January 2014 at 00:00
Getting students on their feet enhances lessons about speed

In the aftermath of a Christmas of inaction, overeating and perhaps even overdrinking, a lesson teaching the concept of speed is probably going to be problematic. You are no doubt feeling rather slow in mind as well as in body.

So leave behind the tired resources recounting the same boring journeys of cars or trains from A to B, which will only add to your inertia, and try something different.

After a brief recap on how to calculate speed from distance travelled and time taken, get groups of students to measure some "fun" speeds: their speed walking down the corridor; the speed of a water droplet trickling down a window pane; the average speed of a ball of paper falling a distance of 2m; the average speed of Harry's repeated excursions to fetch you coffee.

Alternatively, you could take your class outside to the road that goes past your school, measure out a set distance and chart the speeds of cars as they drive past, finding the average and seeing how many are breaking the speed limit. (Following up by reporting licence plate numbers to the local police is optional.)

The question then is: how do we track the movement of an object as the motion changes? Line students up along a corridor or outside, handing out stopwatches every 2m. Get a volunteer to walk slowly down the line at a constant speed. The students with stopwatches measure the time it takes for the volunteer to travel between them. Repeat the exercise with the volunteer walking at a faster constant speed and then gradually accelerating.

Back in the classroom, ask the students to plot three lines on the same axes of distance against time for the three motions. You might want to prepare a few worksheets with pre-drawn axes for students who require extra help.

You can follow this up and assess their understanding by getting them to sketch fractional distance-time graphs on the whiteboard for different motions. I have a running joke with my classes about me not liking dogs, so I ask them to sketch the distance-time graph for a dog being fired into the air from a cannon, a car driven by a dog crashing into a wall and a dog falling from an aeroplane.

For homework, I like to offer a choice of tasks. Perhaps students could measure the speed that a pet moves, including their measurements and a couple of photographs of them doing the homework. Alternatively, I prepare a worksheet personalised for the class, asking them to calculate different speeds. For example, "Janine and David have got married and are walking down the aisle of a church, which is 23m long. It takes them .". Students love it when they are mentioned.

Simon Porter teachers physics for Nord Anglia Education in Poland. Find his lesson PowerPoint here.

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