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Investigation
Lesson – Force - Physics
LESSON PLAN – Force
Name(s):
Evelyn Baldwin
Title of Lesson:
Force and Acceleration
Source of Lesson:
Martin Orr
Lincoln-Way
High School
Length of Lesson:
50 minutes
Description of the Class:
Physics – Mars Rover Curriculum
TEKS Address - Physics:
(2) Scientific
processes. The student uses scientific methods during field and laboratory
investigations. The student is expected to:
(C) Organize, analyze,
evaluate, make inferences, and predict trends from data;
(D) Communicate valid
conclusions;
(E) Graph data to observe
and identify relationships between variables;
(4) Science
concepts. The student knows the laws governing motion. The student is
expected to:
(A) Generate and
interpret graphs describing motion including the use of real-time technology;
(B) Analyze examples
of uniform and accelerated motion including linear, projectile, and circular;
(C) Demonstrate the
effects of forces on the motion of objects;
(D) Develop and
interpret a free-body diagram for force analysis;
I.
Overview
Students
work in groups to determine what the graph of a constant force would look
like. After constructing their graphs, they are able to see what is constant
when the force is constant and what is changing. Also, they can see how mass
plays into a force.
II.
Performance Objectives
The student will be able to:
·
Measure the time it takes a person to travel a
known distance when a constant force is applied
·
Construct a distance vs. time, velocity vs.
time and acceleration vs. time graph for the data collected
·
Interpret the graphs and make predictions
based upon them
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Learn that when a constant force is applied to
a mass a constant acceleration will result
III.
Resources, Materials, and Supplies needed for a class
of 24
For each group of 4:
1 spring balance
1 tow rope
1 coaster cart (an enlarged skateboard)
1 stopwatch
4 lab sheets
For the entire class:
1 measuring tape @ least 15 m long
Masking tape
Overhead
graph
IV.
Safety Considerations
We should make sure the students are careful when pulling each other on
the coaster cart.
V1. Set-up
1.
The data table used by students should contain the
following information:
a.
The distance traveled
b.
The amount of force being applied
c.
The time it takes to travel each distance
d.
The velocity at each distance
e.
The change in velocity (acceleration) at each
distance
2.
The graphs that each student is to make are a
distance vs. time, velocity vs. time, and acceleration vs. time graph. These
can all be put on the same graph, using different color pencils or pens.
3.
The coaster carts can be constructed out of ¾”
plywood or a similar material and roller-skate wheels. Alternatives to
constructing these carts are roller skates, skateboards, or even wheeled
office chairs.
Five E Organization
Teacher Does Student
Does
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Engage:
Time: 5 minutes
Show the shuttle
launch clip to students.
http://www.geocities.com/CapeCanaveral/Launchpad/1499/
Ask the students
the following:
- What just happened?
- How do you suppose the vehicle was
launched?
- What is force? What does a force do?
Tell the
students that we are going to investigate the idea of forces, and that they
need to get into their lab groups.
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Students watch
the video clip
- The space shuttle was launched
- The rockets pushed it up.
- I don’t know. Forces make
things move.
Students get
into their designated groups.
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Explore:
Time: 30 minutes
Explain the lab procedures to the students briefly. (The
directions will be provided on the lab sheet.)
Each student will be pulled by a partner down the hall,
on the coaster carts. Distances of 5, 10 and 15 meters will have already
been marked on the floor. While doing this, another member of the group
will record the time that it takes to travel each designated distance. The
student pulling the cart must maintain the same force reading on the
balance throughout the entire distance (though the reading can be different
for different people). The process is repeated until each member of the
group has had a chance to ride on the cart.
Each student is to plot her own data.
Once the data is plotted, the members of the group
should compare their graphs to one another.
During the exploration, I will ask the groups the
following questions (also, questions similar to these will be on the lab
sheet):
- Is
the distance graph a straight line, what about the velocity line or
the acceleration line?
- What
is the slope of the velocity line and the acceleration line?
- What
is the value of the acceleration line? What does this mean?
- Is
your graph like your partner’s? How are they the same?
Different? Why?
- Based
upon your graphs, predict what will happen to the graphs if there were
two of you on the cart at the same time? Only half of you?
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Students listen
to instructions.
Students work
diligently in their groups, asking any questions if they have them.
Students plot
their own data and compare the different graphs.
Students
compare their graphs to their neighbor’s graphs and note the
similarities and differences.
- The distance is a curved line. The
velocity and acceleration are straight lines, though the acceleration
is flat and the velocity is tilted.
- The velocity has a slope. The
acceleration has a slope of zero (it is flat).
- The acceleration is y = the slope
of the velocity. Interesting. The acceleration is constant.
- The graphs look almost the same,
but the values are different. Maybe they are different because the
forces we used were different.
- Hmm…I don’t know. Let
me look at what my neighbor got.
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Explain:
Time: 10 minutes
After the groups have gathered and analyzed their own
data, we will discuss what we found.
The first thing the students should notice is that their
velocity continued to increase. This will be obvious to them from their
experience of riding on the cart. The students will also have a graphical
representation of what they had experienced while riding on the cart. Ask
one group to show their findings, and to discuss them with the class.
Since each student will have ridden the coaster carts more
than once with a different amount of force being applied each time, they
will also come to the understanding that the more force applied the greater
the acceleration.
When students compare their graphs with that of their
partner’s they will see that everyone experienced a constantly
changing velocity (acceleration). Therefore, a constant force produces a
constant acceleration.
Finally, the students will see that the acceleration
experienced by each one of them was not the same. The difference in the
acceleration that each one of them experienced is related to the amount of
force being applied and the amount of mass to which the force was being
applied (a = F/m or F=ma).
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Students discuss results with the class.
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Extend/Elaborate:
Time: 5 minutes
It is at this
time that we will discuss force diagrams. I will have a volunteer come to
the board and draw the cart. Then I will have another student draw an arrow
indicating the force on the cart. Finally, I will ask the class if there
are any other forces acting on the cart.
After some
discussion, they will realize that gravity is also pulling on the cart. Why
then, is the cart not falling down? Then I will briefly discuss the concept
of the normal force. I will then have student draw arrows indicating the
gravitational force and the normal force. Are these forces equal? Why or
why not?
Finally, if time
permits, I will ask another student to draw the frictional force on the
cart. Is the frictional force equal to the pulling force? Why or why not?
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Students will
participate in the discussion.
One student
will come to the board and draw an arrow showing the force being applied to
the cart.
Students
don’t think there are any other forces.
I remind them
that gravity is acceleration. Then I tell them to look at the force
equation. This leads them to believe that there is a gravity force. They
say they don’t know why the cart isn’t falling down. Maybe
because the floor is in the way.
One student
draws the two forces. They are equal since the cart isn’t moving up
or down.
The student
tries to draw the arrow in the right direction. She may or may not do this
correctly.
Hmm…They
aren’t equal since the cart is moving. The pulling force is greater.
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Evaluate:
No time L
I remind students
to turn in their lab sheets. These will be used as an assessment of
today’s activities.
Furthermore,
they will be assigned homework out of the book dealing with forces.
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Students turn
in their lab sheets.
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