Thank you Ofqual for chucking in another term into the new
physics content that I have never come across before! Most other teacher that I spoke to about it
knew what inertia is but had not ever used the phrase ‘inertial mass’. It turns out inertial mass is just a
re-arrangement of Newton’s second law. SO,
once I knew that the next conundrum is how to teach it in a way that’s going to
keep students engaged. At this point I
must thank old Top Gear which was being repeated on Dave. For whatever reason they were drag racing and
the idea to base this lesson around was born!
Pre-Starter
I am fortunate enough to have a long corridor outside my
room, so as the lesson is based around drag racing it would have been criminal
not to have used it! Before students
entered the room, I asked them to line up along both sides of the corridor. At one end I set up a ramp and used four
different cars, all different masses. I
asked students to describe what they thought would happen in terms of distance
travelled, acceleration and other forces.
We set the cars off down the ramp and saw what happened. This activity worked well and got students in
the correct frame of mind to approach the lesson with.
Starter
As a concept, inertial mass is something that I had never
come across, so it’s a safe bet that my students hadn’t. To help students gain a basic understanding
of what inertial mass is and where it comes from I used a tried and tested
literacy game. It’s always important in
a lesson to ensure that your students have had to read something as it helps
re-enforce expectations and as we all know, the more students read the better
their reading age becomes, and the better their reading age the greater
progress they are likely to make within their own journey. I start off by giving students some
information on the development of the idea of inertial mass to read. Depending on the level of your students you
could allow them to highlight key points or briefly talk to them before they
start of what they need to look out for.
If you have a low ability class, you could almost turn this into a group
reading exercise if you have the time.
Once your students have finished reading they can play snakes and
ladders. DO NOT ASSUME ALL STUDENTS KNOW
HOW TO PLAY SNAKES AND LADDERS! After
students, have finished make sure that you leave some time to ask specific
students answers to some of the key questions to ensure that they have got out
of the task what they need. By running
this literacy activity as a game, it almost stops students from putting up any
barriers to reading that they may if just given some information to read.
Task 1
Hopefully by now, your students should have some
understanding about what inertial mass is, however, I always find that it never
does any harm to go over the basics of it again. This will also allow you to introduce the
idea that force in terms of inertial mass is the amount of force it takes to
get an object moving. In this task, I
like to get students to manipulate newton’s second law equation using an
equation triangle, to construct the equation for inertial mass. Once students have the equation they will
need a chance to do some calculations using it.
You could give students a list of questions to work through which would
do the trick but would be very dull. The
way that I like to approach this type of task is to let students work in pairs,
rolling a dice to pick which question to answer. After giving students enough time to have a
go at working out three or four, pick specific students to give you the answers
to the six questions. As they give you
the answers, note them down on the board as you will be using them in the next
task.
Task 2
It’s at this point in the lesson that you bring it back to
looking at inertia in relationship to drag racing b carrying out the slowest
drag race in history! Set up the four
cars of different masses on a table, and attack a Newton meter to each of
them. Get four students to pull the four
cars forward, recording the reading on the Newton meter at the point when the
car just started to move. This will give
you a value for the force of each car.
You can then tell students how quickly the cars are accelerating so the
inertial mass for each can then be calculated.
This activity is designed to help students see what inertial mass is and
will ensure that they have full confidence in using the equation. This activity will also give the lesson
another element which helps keep students engaged in the lesson.
Task 3
Now that students are happy that they can calculate the
inertial mass of an object, they can start to look at how inertial mass and
force are connected. Ask students to
quickly get down a table with what they worked out earlier in the lesson, and
include an extra column for momentum as they will be using it later. Once students have these results down ask
them to sketch a graph of force against inertial mass in their books. This graph does not have to be precise as
students just need to be able to comment on the relationship between these two
variables. If you had a lower ability
class, you could sketch the graph on the board and then discuss what it shows
as a class. Students need to be able to
explain that as inertial mass increases so does the amount of force required to
get an object moving. Once students can
describe the relationship between inertial mass and force, they can start to
think about how momentum is related to inertial mass.
Task 4
Now that your students can work out inertial mass, momentum
& have recalled how to work out acceleration I thought that I would take
the opportunity to connect them to calculating acceleration from a speed time
graph. Dependent on the level your
students are working at you may need to fully explain how to calculate
acceleration from a graph again, however with a high ability class you can
leave them to it. After you have
explained the task to students I placed six of these questions around the room
for students to work through. By placing
the questions around the room, it got students up out of their seats so added
another element into the lesson.
Plenary
The type of plenary I used for this lesson was quick and
simple. All I asked the students to do
was to describe the inertial mass, momentum and the effect they would have on
stopping distance to each other. First
get students into groups of four then give each student a vehicle to talk
about. Give them a bit of time to decide
what they are going to say then set them off.
Whilst students are working circulate so you can assess how much they
have learnt.
By the end of the lesson I found that my students understood
the content and at the same time had a bit of fun. One word of warning, students may start
making car noises at various points during the lesson!
You can follow me on twitter @teacherchalky1 or on Facebook
@teachlikeahero.
Thanks for reading
D Chalk
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