Spike Prime - Pulleys for Lifting Weights

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Let's begin

Possibly by 1500 BC people in Mesopotamia used rope pulleys for hoisting water. Archimedes of Syracuse invented the first compound pulleys 287 BC - 212 BC. Plutarch reported that Archimedes moved an entire warship, laden with men, using compound pulleys and his own strength. read more...

In this exercise, we will observe how pulleys can make a very hard work easier. How could heavy objects be lifted using less force? A very useful skill when you are to build a house or a church...

Build

Model:

The basic model uses a compound pulley, but it can be easily modified to skip one or both pulleys as shown in the pictures below.

Pictures:

Building instructions:

• Pulleys (PNG)

Download building instructions:

• crane with pulleys (pdf)

Download stud.io model:

• pulleys (stud.io)

Program

Download: pulleys.llsp

The program starts increasing the power of the motor and observing when it will start moving. If it moves by 1/4 of rotation, it assumes that the power to lift the cargo is sufficient, shows the lift direction, and lifts the cargo to the second floor, where it is detected by a color sensor. After the cargo is unloaded, the cabin is moved back to the first floor, where it is detected using the ultrasonic sensor.

Measure, analyze, think

• Observe the number of rotations of the motor needed when using different number of pulleys. Can you derive this relation?
• Measure the required power required for different cargo weights, and for different number of pulleys used.
• Record your own measurements, create a table, and a chart.
• What did you notice about the relation between the power required, the number of pulleys used, and the weight of the cargo?
• Perform measurements with your model and discuss in your group what has happened.

Explore and modify

• Modify the program so that the color sensor will use the color instead of reflected light in order to get a better stopping behavior. Modify it also to take the number of pulleys into account so that the cabin will always stop when reaching the bottom station properly, regardless the number of pulleys.
• If you have sufficient parts, try to create even more complex pulleys.

Present

• Prepare a short presentation for other groups. Tell others about how your measurement went, what issues did you have to solve. What do they mean and why did they happen?

Additional resources

• Download: Pulleys - all media files