Physics · Grade 12

Active learning ideas

Non-Conservative Forces and Energy Loss

Students retain the abstract concept of energy loss best when they feel heat from friction, hear the sound of a sliding block, and see energy bars drop in simulations. Active labs make the invisible work of non-conservative forces visible and memorable.

• Ontario Curriculum Expectations
• HS.PS3.D.1

• 30–50 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Problem-Based Learning
• 45 min · Pairs

Lab Rotation: Friction Incline Stations

Prepare three inclines with smooth wood, sandpaper, and carpet surfaces. Pairs release a cart from fixed height, measure bottom speed with photogates, and calculate percent energy loss for each. Groups compare data and identify friction coefficient trends.

Differentiate between conservative and non-conservative forces.

Facilitation Tip

At each Friction Incline Station, place a small infrared thermometer on the block so students see temperature rise as soon as motion starts.

What to look for

Present students with three scenarios: a ball falling in a vacuum, a block sliding down a rough incline, and a pendulum swinging in air. Ask them to identify which scenarios involve non-conservative forces and explain why, referencing the conservation of mechanical energy.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 02

• Problem-Based Learning
• 35 min · Small Groups

Pendulum Damping Challenge

Students set up pendulums with steel balls in air versus submerged in viscous fluid. In small groups, they time swings over 20 cycles, plot amplitude decay, and compute mechanical energy loss per cycle using height measurements.

Analyze how non-conservative forces affect the total mechanical energy of a system.

Facilitation Tip

Have students mark the amplitude of each swing on the board during the Pendulum Damping Challenge so the decay curve becomes a visible class artifact.

What to look for

Provide students with a problem where a block slides a specific distance on a surface with a known coefficient of kinetic friction. Ask them to calculate the work done by friction and the resulting change in the block's mechanical energy.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 03

• Problem-Based Learning
• 30 min · Whole Class

Whole Class: Energy Loss Debate

Present collision videos with and without friction. Whole class votes on energy accounting, then breaks into pairs to calculate losses using initial/final speeds and masses. Reconvene to resolve discrepancies with whiteboard models.

Calculate the energy dissipated by friction in a given scenario.

Facilitation Tip

Assign roles in the Energy Loss Debate (recorder, timekeeper, evidence presenter) so every voice contributes to the discussion.

What to look for

Facilitate a class discussion using the prompt: 'Imagine designing a roller coaster. How would you account for energy loss due to friction and air resistance to ensure the cars complete the track and provide a thrilling ride?'

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 04

• Problem-Based Learning
• 50 min · Individual

Individual: Ramp Design Optimization

Individuals design a ramp to minimize energy loss for a marble reaching maximum distance. Test prototypes, measure kinetic energy at launch, iterate based on friction calculations, and share final designs.

Differentiate between conservative and non-conservative forces.

Facilitation Tip

Provide graph paper and colored pencils for the Ramp Design Optimization so students can overlay energy vs. distance curves for different surfaces.

What to look for

Present students with three scenarios: a ball falling in a vacuum, a block sliding down a rough incline, and a pendulum swinging in air. Ask them to identify which scenarios involve non-conservative forces and explain why, referencing the conservation of mechanical energy.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

A few notes on teaching this unit

Start with the pendulum because its clear decay is easy for students to measure and graph. Use the ramp labs to challenge the idea that friction is ‘just slowing things down’ by showing students that work done by friction actually heats the block. Avoid long derivations of formulas—instead let students discover the relationship between distance, friction, and energy loss through measurement and graphing.

Students will correctly identify non-conservative forces in real devices, quantify energy loss on ramps, and justify why total mechanical energy falls over time. They will articulate how heat and sound are the ‘missing’ energy forms.

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Watch Out for These Misconceptions

• During Lab Rotation: Friction Incline Stations, watch for students saying ‘friction destroys energy’ when they see the block stop.

  Place an infrared thermometer on the block before and after each trial; students should record the temperature rise and label it as ‘thermal energy added to the block,’ linking the lost mechanical energy to a measurable form.

• During the Energy Loss Debate, listen for claims that mechanical energy is always conserved.

  Ask groups to post their final mechanical energy values from the incline labs on the board; the consistent drop will prompt students to revise their statements and connect the data to the work-energy principle.

• During Ramp Design Optimization, hear students argue that all ramps do the same amount of friction work regardless of length.

  Have teams plot work done by friction against ramp length; the linear relationship will reveal path dependence and correct the misconception.

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Methods used in this brief

• Problem-Based Learning