# Calling all physics teachers: interesting kinematics lessons?

## Main Question or Discussion Point

I am not sure where else to post this. Hopefully this is not in the wrong place.

I am student teaching in a physics classroom this week. I will be teaching about scalars vs. vectors, calculating average velocity, and calculating acceleration.

As I plan my lessons, I've realized they are very boring. Does anyone have any resources I can use to hook the students' attention? Thanks!

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jedishrfu
Mentor
Flavor your talk with fanciful real world examples and demos. I once had to give a talk on Newton's third law F=MA and so I included the case of the benevolent truck stopper.

You see a truck starting to roll down hill and the question should you try to stop it? The truck was 1 ton and it just starts roll on 10degree incline. First I had to determine how much I could push back by pushing a scale against the wall. Next I calculated how force would be needed to stop the truck.

You might use the tortoise and the hare story to discuss average velocity vs instantaneous velocity...

bcrowell
Staff Emeritus
Gold Member
Discussion question (students break up into groups):

Would it make sense to define a zero vector? Discuss what the zero vector's components, magnitude, and direction would be; are there any issues here? If you wanted to disqualify such a thing from being a vector, consider whether the system of vectors would be complete. For comparison, can you think of a simple arithmetic problem with ordinary numbers where you need zero as the result? Does the same reasoning apply to vectors, or not? From your group, have the leftmost person act as zero's advocate and the rightmost argue against letting zero in the club. The rest of the group should act as jurors.

Books typically define a vector as something that has magnitude and direction, but physicists really define it as something that behaves a certain way under rotation. If you have a document camera, bring a queen from a playing card and show that it doesn't behave as either a scalar or a vector: when you rotate it by only 180 degrees, it's the same.

Thank you both for the ideas! I should have mentioned in my original post that this is a grade 11 class and it is sort of a remedial class. I will definitely use the zero vector idea with university students, but I feel it might be too advanced for my current class.

I love the idea of the hare and the tortoise!

Andy Resnick
I am student teaching in a physics classroom this week. I will be teaching about scalars vs. vectors, calculating average velocity, and calculating acceleration.
A lot depends on what your 'goals' for the students are. Since this is a remedial class, you could easily spend the time simply talking about ratios and units: presumably most students are comfortable with the number 3/5, or even 3/5.00, but do they understand what (3 meters)/(5 seconds) means? Similarly, you could pose the questions: If I travel 25 miles in 45 minutes, what is the interpretation of (25 miles)/(45 minutes)? Is this a number? What about something like (4 yards)^2 or (3 feet)/(5 minutes)^2?

Another discussion could center on the difference(s) between average velocity and instantaneous velocity: if you run around a racetrack once in 1 minute, what is your average velocity? (there are multiple possible answers).

Vectors can be painlessly introduced in terms of maps and directions- ask the students how to get from 'here' to (say) the nearest McDonalds, and draw the map as they give you directions.

jedishrfu
Mentor
There are also sports analogies that you could bring in like pitcher pitches a ball at x meters/sec and batter hits ball into the outfield or soccer player kicks the ball... Could show how gravity applies to the mix.