Engineering activity
Pulley Power
Make a simple pulley from a thread spool and string to lift a bucket of toys. Discover how pulling down can lift things up!
Materials and setup
- string
- thread spools
- pencils
- small cups
- coins
- tape
How this changes by age
Pre-K (ages 3–4)
Make a simple pulley from a thread spool and string to lift a bucket of toys. Discover how pulling down can lift things up!
Steps
- Thread a string over a thread spool or empty tape roll held by a pencil.
- Tie a small bucket (plastic cup) to one end of the string.
- Put a small toy in the bucket.
- Pull the other end of the string down. What happens to the bucket?
- Try lifting the toy without the pulley — just picking it straight up. Which is easier?
- Tell a grown-up one thing that surprised you.
Learning objectives
- Discover that a pulley changes the direction of a pull
- Observe that pulling down can lift things up
- Practice threading and tying basic knots
Kindergarten (ages 5–6)
Build a pulley crane to lift a load of coins from the floor to a tabletop. Test with one pulley and then two pulleys — which is easier?
Steps
- Build a crane arm from a cardboard tube taped to the edge of a table, hanging over the side.
- Thread a string over a spool at the end of the arm. Tie a cup to one end.
- Put 10 coins in the cup. Pull the string to lift the load. Is it hard or easy?
- Now add a second spool at the bottom, attached to the cup. Run the string around both.
- Lift the same load with two pulleys. Does it feel lighter?
- Draw both setups and write which one was easier to lift with.
- Tell a grown-up one thing that surprised you.
Learning objectives
- Build single and double pulley systems
- Discover that more pulleys make lifting easier
- Compare effort needed with different pulley configurations
Early elementary (ages 6–8)
Engineer pulley systems with 1, 2, and 3 pulleys. Measure the force needed to lift the same load with each setup. Discover mechanical advantage.
Steps
- Build a pulley frame from a cardboard box or wooden dowels.
- Create pulleys from thread spools on pencils or wooden skewers.
- Setup 1: Single fixed pulley. Lift a load of 10 coins. Measure string pull force with a rubber band scale.
- Setup 2: Add a movable pulley. Measure the force again for the same load.
- Setup 3: Add a third pulley. Measure force again.
- Record results in a table. Calculate: force with 1 pulley vs 2 vs 3. What pattern do you see?
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Measure and compare forces across different pulley configurations
- Discover the concept of mechanical advantage through experimentation
- Record data systematically and identify numerical patterns
Upper elementary (ages 8–10)
Design compound pulley systems and calculate theoretical vs actual mechanical advantage. Explore the trade-off between force reduction and rope length.
Steps
- Research mechanical advantage: MA = load / effort. For ideal pulleys, MA = number of rope segments supporting the load.
- Build systems with 1, 2, 3, and 4 pulleys. Measure effort force for each using a spring scale or rubber band ruler.
- Calculate theoretical MA for each setup. Compare to actual measured MA.
- Measure how much rope you pull for each setup to lift the load the same height.
- Graph: MA vs rope length pulled. What is the trade-off?
- Calculate efficiency: actual MA / theoretical MA. Why is it less than 100%?
- Design a system to lift a 1-pound object using less than 4 ounces of pull force.
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Calculate theoretical and actual mechanical advantage of pulley systems
- Analyze the force-distance trade-off in simple machines
- Measure system efficiency and identify sources of energy loss (friction)
Safety and evidence note
Read the full activity before beginning. An adult should supervise tools, heat, food, outdoor work, movement, and experiments as appropriate. Completion records that the activity was done; the child’s explanation, work sample, photo, or demonstration is stronger evidence of learning than a completion check alone.
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