Download Newtons 1st Law lesson plan

Science Lesson Plan
Newton’s First Law
Lesson provided by Richard Worsey, Head of Science Faculty
Background
Once upon a time an apple fell from Sir Isaac Newton’s Tree.
I took this photograph of a descendent of this very tree at Isaac
Newton’s house, Woolsthorpe Manor in England. Isaac Newton
was a famous English scientist. He studied and observed how
objects move. He wrote one of the most important mathematics
books in history: Philosphiae Naturalis Principia.
Newton’s First Law is particularly challenging to students, as it essentially comes in two parts. One
part predicts the behaviour of moving objects; the other part predicts that of stationary objects.
Difficulties are then further compounded by a link to inertia.
My approach is to eliminate some of the misconceptions that surround the law by bringing them to
the fore in open discussion. A common misception is that sustained motion requires a sustained
force. Another one is that an object is always at rest when the forces are balanced.
The key approach in this lesson is to get beyond the law as a statement and to understand its
implications and links to motion observed in everyday life. Once the law is better understood,
inertia can be brought into play and the law rewritten as a statement of inertia.
The associated Boardworks PowerPoint also provides a link to other topics such as interpretation
of velocity vs time graphs and terminal velocity.
Approach
The objectives of this lesson are;
1) To understand and be able to interpret Newton’s First Law of Motion.
2) To demonstrate this understanding by applying it to challenging and novel situations.
Equipment required:
• ramp and support • spring loaded motion trolley
• ball bearing
• plasticine
• foam
• high shutter speed video camera (optional)
Boardworks Ltd
The Gallery
54 Marston Street
Oxford, OX4 1LF
• paper
• cotton thread
• masses for parachute
• Loggerpro software
or other tracking software
such as Tracker.
FREE
sample material
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Science Lesson Plan
Newton’s First Law
The Activity
This activity involves two main parts. First, the
students will see and analyse a collision video
clip, and then perform two experiments to further
study collisions in terms of Newton’s First Law.
The second part considers terminal velocity in
the context of a parachute falling.
Collisions
Show an NCAP safety collision video clip – You
Tube has a proliferation of these. An example can
be found at http://www.youtube.com/watch?v=5VqI
IcUDxRI&feature=fvsr
Newton’s F
irst Law, slid
e2
Once the class has viewed the video, ask the students
two questions - provide no hints and generate a discussion
without correcting any misconception at this stage.
1) Is a passenger thrown forward in a front end car crash?
2) Is a passenger’s head thrown backwards if a car is run into from behind?
Once each student has decided on an answer, ask for their
justification – again providing no hints as to whether they
are correct or incorrect.
Show slide 2 (free to download) from the
Boardworks PowerPoint ‘Newtons First Law’.
Explain (or recap) what is meant by weight and
reaction forces. Using the animation on slide
2, discuss how the forces affect each of the
motions and how these might change if the
size of individual forces is altered. Talk about
balanced forces and how these can cause an
object to stay at rest or remain at a constant
velocity. Use slide 3 (free to download) to
summarise this discussion as Newton’s First
Law.
Newton’s F
irst Law, slid
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Science Lesson Plan
Newton’s First Law
Without further explanation, offer the students a chance to revise their answers and justifications to
the two questions set at the beginning of the lesson based on their new understanding.
To further explore these questions, set up the following two experiments. It is useful to video the
experiments with a high-speed shutter and then capture frames to explain what is happening in
the experiment.
Experiment 1: front end crash
Set up the experiment as shown in Figure 1. Release the trolley down the slope. Ensure that the
ball bearing is free to move within the plasticine dish. As the trolley collides with the foam, the
ball continues to move forwards, as there is no resultant force acting upon it. Ask the students to
observe the ball bearing.
Figure 1.
Experiment 2: rear end crash
Set up the experiment as shown in Figure 2. Compress the spring and release the trolley. The
ball bearing should be free to move as the trolley is released initially. The ball bearing remains
stationary, as there is no resultant force acting upon it.
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Figure 2.
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Science Lesson Plan
Newton’s First Law
Figure 3 shows some example frame captures from Experiment 2.
1. Trolley moving left to right just
prior to collision.
2. Trolley moving left post collision.
Note position of ball bearing relative
to wall.
3. Trolley moving left post collision.
Note position of ball bearing
relative to wall.
4. Trolley moving left post collision.
Note position of ball bearing relative to
wall.
Figure 3.
Key concept – an object will remain at rest or remain in motion unless acted upon by an
unbalanced (resultant) force.
Parachute
Another misconception can arise that needs to be
dealt with here – an object is always at rest when the
forces are balanced.
In the context of a skydiver reaching terminal
velocity, slides 4 and 5 (free to download) from
the Boardworks PowerPoint will address this.
Play the parachute animation on slide 4 and
discuss with the students what happens as the
resistive force alters due to acceleration (this can
be related to everyday experience e.g. resistive
force as you accelerate downhill on a bike). Use
the data produced to graph (slide 5) and discuss
what each section of the graph represents.
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Newton’s F
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Science Lesson Plan
Newton’s First Law
Students can now investigate this for themselves via
a parachute experiment. They can make their own
parachutes from simple materials such as paper,
cotton thread and weights to explore how different
factors, such as drag surface area and mass, affect
motion. Consider using tracking software to analyse
a video of the descent of different parachutes to
compare the variables.
An alternative to the parachute experiment is to
product the graph first from slide 5 and then verify
using the Boardworks animation, slide 4.
Newton’s F
irst Law, slid
e5
Taking it Further
The natural extension of this lesson is to introduce inertia – the
reluctance of an object to move. This can be done by pulling paper from under two cans (one
heavy and one light but not telling the students which is which!). Place these cans on trolleys and
ask students to push them then relate to inertia.
Outcomes/Benefits
If the learning objectives have been achieved, students will now understand Newton’s First Law. A
good way to check this is to ask the students to rewrite it in a different form.
Some ‘thought’ questions for homework:
• If you were repairing the Hubble Telescope and pushed away from it to return to your space
shuttle how could you create the additional force needed to keep you moving towards the shuttle?
• Many cars have headrests. How do these prevent neck injuries? Explain your answer in terms of
Newton’s First law.
• Explain in terms of inertia why you should zigzag as you run away from an elephant.
Or
Boardworks Ltd
The Gallery
54 Marston Street
Oxford, OX4 1LF
d
r FREE Sampl
You
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t: 0845 0 300 400
f: 0845 0 300 200
[email protected]
www.boardworks.co.uk