Inclined Planes and Pulleys
Force, Motion, and Energy
Inclined Planes and Pulleys
Background
Simple machines are devices that change the direction of a force applied on an object or reduce
the amount of force needed to move an object. Forces are measured in Newtons using a spring
scale. There are six basic simple machines: lever, inclined plane, wheel and axle, screw, wedge
and pulley. In this activity, you will learn about the inclined plane and pulley.
Inclined Plane
An inclined plane is a slope or ramp that requires less force because objects slide over a longer
distance as compared to lifting objects straight up over a shorter distance. Applying a smaller force
for a longer distance makes the task seem easier. Examples of inclined planes are pictured below.
Pulley
A pulley is a wheel with a groove down the middle that allows for a rope to be wrapped around it
without it falling off. The pulley can make it easier to move an object by changing the direction of
the force you are applying or by decreasing the amount of force needed to move the object. There
are two types of pulleys: fixed and movable. A fixed pulley is attached to something and allows for
you to change the direction of the force. A moveable pulley decreases the amount of force needed
because you can pull with less force for a longer distance.
Load
When simple machines are
used to move an object, the
object itself is called the load.
Answer the Background questions in your Student Journal.
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Inclined Planes and Pulleys
Force, Motion, and Energy
Part I: Using an Inclined Plane
In this activity, you will accomplish the task of raising a mass to a distance of 10 cm above the
table top with and without the use of a simple machine, the inclined plane.
1.  Put 300 g of sand in a plastic bag and seal it. Put the binder clip on the bag so you can hang
the bag from the spring scale during the investigation.
2.  Mark the one meter board at 0 cm, 20 cm, 40 cm, 60 cm and 100 cm using a meter stick.
3.  Stack the textbooks so that they are 10 cm high.
4.  Hook the bag of sand to the spring scale and lift the mass straight up to the 10 cm level of the
pile of books to get a force reading without the use of a simple machine.
5.  Lean the board against the 10 cm high pile of books such that the 20 cm mark rests against the
top of the book pile and the 0 cm line is at the bottom of the ramp. One group member will have
to hold the board in place. The distance the load travels is now 20 cm in order to raise the load
10 cm above the table height.
6.  Measure the angle using a protractor at the base of the inclined plane. Note: it should be less
than 90°.
7.  Pull the mass up the ramp at a constant speed. It is important to keep the spring scale parallel
to the ramp. Stop at the 20 cm mark on the board that corresponds to a distance of 10 cm
above the tabletop.
8.  Measure and record the force on the spring scale on the Inclined Plane Data Table in your
Student Journal.
9.  Repeat steps 1 through 7 for the 40 cm (or 0.40m) and 60 cm (or 0.60 m) ramp.
Answer the Part I questions in your Student Journal.
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Inclined Planes and Pulleys
Force, Motion, and Energy
Part II: Using a Pulley
In this activity, you will accomplish the task of raising a mass to a distance of 10 cm above the floor
with and without the use of a simple machine, the pulley.
A
1.  Construct the load bucket of the pulley using the cup, a hole
punch, and 20 cm of the twine. Punch a hole about 2 cm from the
rim on opposite sides of the cup. Use 5 cm of each end of the 20
cm length of twine to assemble a handle on the cup. Insert each
end through the holes in the cup and tie a knot to secure the
handle in place. Hook a paperclip on the handle.
B
2.  Place the bag with 200 g of sand in the cup. Use the spring scale
to lift the load bucket a distance of 10 cm above
the floor and record your measurement in the data table on the
Pulley Data Table in your Student Journal.
3.  Place the 30 cm 2 x 2 board on a flat table surface. Be sure
that the end with the eyehook attached to the board is at least 8
cm off the end of the table. Secure the board onto the table with
duct tape. See diagram A.
4.  Assemble a single, fixed pulley system. Be sure to make a loop
on each end of the rope and secure it with duct tape. Attach
one end of the rope to the paperclip on the bucket and the other
end of the rope to the spring scale.
C
5.  Lift the bucket using the single, fixed pulley. Make sure to pull on
the scale until the bucket has been lifted off the ground a distance
of 10 cm. See diagram B. Record the force required
to lift the bucket with the pulley in the data table of your Student
Journal.
D
6.  Assemble a single, moveable pulley system and lift the load. See
diagram C. Record the force required to lift the load using the
single, moveable pulley in the data table of your Student Journal.
7.  Assemble a system that contains both a single, fixed pulley and a
single, moveable pulley and lift the load. See diagram D. Again,
record your observations in the data table of your
Student Journal.
Answer Part II and Reflections and Conclusions questions in your Student Journal.
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