Physics · 12th Grade

Active learning ideas

Applications of Newton's Laws: Pulleys and Systems

Active learning works for pulleys and connected systems because students often struggle to visualize forces across multiple objects at once. Moving, measuring, and discussing real systems makes the abstract concrete, helping students see how shared variables like tension and acceleration tie the equations together.

• Common Core State Standards
• HS-PS2-1

• 40–60 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Peer Teaching
• 40 min · Pairs

Peer Teaching: The Atwood Machine Analysis

Pairs work through an Atwood machine (two masses over a pulley). One student sets up free-body diagrams and writes Newton's Second Law for each mass; the other explains the tension and acceleration relationships. They swap roles for a different mass configuration and compare predictions to measured accelerations.

Analyze how tension forces are transmitted through ropes and pulleys in a system.

Facilitation Tip

During the Atwood Machine Analysis, circulate and ask groups to explain how their free-body diagrams connect through the same tension and acceleration values.

What to look for

Provide students with a diagram of two blocks connected by a string over a single fixed pulley. Ask them to draw separate free-body diagrams for each block and write the corresponding Newton's Second Law equation for each, identifying the common tension and acceleration variables.

• Understand
• Apply
• Analyze
• Create
• Self-Management
• Relationship Skills

Activity 02

• Inquiry Circle
• 60 min · Small Groups

Inquiry Circle: Mechanical Advantage Pulley Lab

Groups build simple and compound pulley systems using ring stands and spring scales. They measure the force required to lift a given weight with each configuration, calculate the mechanical advantage, and explain what trade-off (pulling distance) compensates for the reduced force needed.

Predict the acceleration of a multi-object system using free-body diagrams and Newton's Second Law.

Facilitation Tip

In the Mechanical Advantage Pulley Lab, ensure students measure forces with spring scales only when the system is in equilibrium to avoid dynamic errors.

What to look for

Present a scenario with a movable pulley lifting a 10 kg mass. Ask students to calculate the minimum applied force required to lift the mass at a constant velocity, assuming an ideal pulley system. They should briefly explain their reasoning.

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Activity 03

• Gallery Walk
• 45 min · Small Groups

Gallery Walk: Connected System Problem Sets

Post 6 different connected-object scenarios around the room (two masses over a pulley, a block on a ramp connected to a hanging mass, etc.). Groups rotate and write the system equations for each scenario without solving, then reconvene to solve one problem collectively as a class.

Design a system of pulleys to lift a heavy object with a reduced applied force.

Facilitation Tip

For the Gallery Walk, require students to annotate their problem sets with clear labels for tension and acceleration before sharing with peers.

What to look for

Pose the question: 'How does adding a second, identical block to the system described in the quick-check activity change the acceleration and the tension in the connecting string? Explain your reasoning using Newton's Laws.'

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

A few notes on teaching this unit

Experienced teachers approach this topic by having students work in small groups to solve scaffolded problems first, then gradually increasing complexity. Avoid giving away solutions too quickly, as the process of setting up simultaneous equations is the core skill. Research suggests that whiteboarding solutions in front of the class helps students see the connections between their peers’ reasoning and their own.

Successful learning looks like students correctly drawing separate free-body diagrams for each object, writing Newton’s Second Law for each, and solving the resulting system of equations. Students should also explain how tension and acceleration connect the objects in their analysis.

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Watch Out for These Misconceptions

• During the Atwood Machine Analysis, watch for students who think tension changes as it passes over the pulley.

  Have students use two spring scales on either side of the pulley in the lab setup and observe that they read the same force in equilibrium. Ask them to explain why this confirms tension is uniform in an ideal rope.

• During the Mechanical Advantage Pulley Lab, watch for students who believe both objects in a connected system experience the same net force.

  Direct students to draw separate free-body diagrams for each mass and write Newton’s Second Law for both. Ask them to compare the net force expressions and discuss why they differ despite the shared acceleration.

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Methods used in this brief

• Peer Teaching
• Inquiry Circle
• Gallery Walk