EASY DOES IT
This lesson will provide students with an understanding of how
inclined planes make work easier and the relationship between distance and
force. The students will measure the force needed to move a model car a
certain distance. The students will also measure the force needed to move
a model car the same distance along an inclined plane. The students will
make mathematical predictions based on the formula W = f x d and prove their
predictions through experiments, demonstrating their knowledge of the distance
and force relationship.
Simple Machines: Working Together (Coronet Films)
Bill Nye, The Science Guy: Simple Machines (KCTS/Seattle)
Students will be able to:
- demonstrate knowledge of the formula, W = d x f;
- compare the relationship between distance and force;
- compare hard work to the ease of work with simple machines.
Per group of three:
- chart paper
- definitions with pictures
- spring scale
- model car with detachable wheels
- box, height determined by teacher (9 in.)
- three inclined planes of various lengths (18, 36, 45 in)
- distance - a gap, space between two intervals
- force - the push or pull needed to move an object
- friction - resistance to motion
- inclined plane - a slanting or sloping surface used to raise an object
to a higher level
- load - the object being lifted or moved by machine
- machine - any object that changes the force a person exerts on it
- work - when a pushing or pulling force moves something with weight
through a distance
The vocabulary words will be written out with pictures to demonstrate
the words. They will be placed around the room. Student volunteers will
be asked to read each one. Students may volunteer some machines we use in
The focus for viewing is a specific responsibility or task(s)
students are responsible for during or after watching the video to focus
or engage students' viewing attention.
Say, "Today we are going to learn about inclined planes, otherwise
called ramps, that are a simple machine. We will learn how they work and
how they help us to use less force." Say, "Can you see in the
video two other machines that are inclined planes other than a ramp?"
BEGIN the video Simple Machines: Working Together immediately
after opening credits showing a cartoon cave with a tree on the left. PAUSE
the tape after narrator says, "but to scientists, work means something
special." Ask if anyone can tell us what work is. (Use vocabulary definitions
as a reminder if needed.) RESUME video, PAUSING after, "with
all simple machines, the input work and the output work are equal, except
for small losses through friction." Ask, "what is friction?"
(Again, refer to vocabulary if needed.) Ask, "what kind of loss would
you expect if there were no friction? What might happen?" RESUME
the video and PAUSE after, "so for all simple machines the input
force X and its distance are equal."
Write w = d x f on chart and review with students. Give examples such as:
if w = 18, what could d x f equal? (9 x 2, 18 x 1, 3 x 6). RESUME
the tape and PAUSE after "only their products have to be the
same." Ask, "what is a product?" (The answer in multiplication.)
Say, "so if I have a force of 3 pounds and a distance of 2 feet, what
would my product be?" (Point out that answers must be in foot pounds,
answer 6 ft. lbs.) Ask, "Can anyone give a different output force and
distance to equal 6 ft. lbs.?" (accept 6 x 1 or 1 x 6) RESUME
the tape. PAUSE after, "six times what equals 120?" (answer
20) RESUME tape and STOP after the caveman is knocking his
head with his finger and says, "you can control the amount of the trade."
Change tape, insert Bill Nye, The Science Guy: Simple Machines. BEGIN
the tape as Bill Nye slides down a fire pole and after reaching the bottom
says, "using the fire pole is a fast and fun way to get down here,
but using it to get back is another story." PAUSE after he says,
"this is too much work." Ask, "what work is he talking about?"
Help students relate this to the force needed to pull himself a distance
up the pole. RESUME video and PAUSE after Bill Nye says, "we
could use a ramp." Ask, "does anyone know what a ramp is?"
Help students recognize it as an inclined plane. RESUME video and
stop after the child's experiment with ramps and books as he says, "cool."
STOP tape at the screen saying, "ramps equal less force."
Ask if anyone can explain how ramps equal less force. Remind students to
think about w = d x f.
Divide the class into groups of three. Pass out materials. Have
the students attach the spring scale to the car and measure the force needed
to lift the car straight up to the top of the box. Record the force needed
and the distance lifted on the worksheet. Complete the formula w = d x f.
Experiment #2 worksheet: Using the shortest ramp, measure the ramp and fill
in under "d" on the worksheet. Attach the spring scale to the
model car and place the car at the end of the ramp as seen in the picture.
Pull the car up the ramp to the top of the box. Record the force needed
to pull the car up the ramp and enter it in the formula under "f."
Complete the formula to find out how much work was needed to pull the car
up the shortest ramp.
Experiment #3 is completed the same as #2 using the middle-sized ramp.
Experiment #4: Measure the longest ramp. Predict the force that will be
needed to pull the car up the ramp. Test your prediction by pulling the
car up the ramp following the same directions as Experiment #2 and #3.
Complete the questions included in the experiments.
Plan a neighborhood walk looking for inclined planes.
Have a car race using different length ramps, vs. different weighted cars
and same distance ramps.
Invite a carpenter to discuss the construction and uses of ramps, and the
formula used to determine the appropriate distance and angle of ramps.
Language Arts: Write a story of how the first use of a ramp
came to be.
Math: Calculate what distance a ramp should cover for the force to be 1,
2, 3, 4 or 5 pounds for a work load of 60 ft. lbs. Make up other combinations.
Given the work and distance, calculate the force. Given the work and force,
calculate the distance.
Social Studies: Research the earliest inclined planes, people who used them,
and the work they were doing.
Master Teacher: Mary Hanson
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worksheet associated with this lesson.
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