Physics · Year 11

Active learning ideas

Work Done by a Constant Force

Students retain the vector nature of work best when they physically feel the difference between pushing straight ahead and pulling at an angle. Active tasks let them link the abstract formula W = F d cosθ to real sensations of effort and motion, turning a tricky cross-topic idea into a lasting understanding.

• ACARA Content Descriptions
• AC9SPU06

• 25–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Think-Pair-Share
• 35 min · Pairs

Pairs Pull: Angle Effects on Work

Pairs attach a force meter to a toy car and pull it across a table at 0°, 30°, 60°, and 90° using a protractor. Record force, measure displacement, and compute work with cosθ. Graph work versus angle to spot the cosine pattern.

Explain why a force perpendicular to displacement does no work.

Facilitation Tip

During Pairs Pull, ask each pair to plot their measured work versus angle on a shared whiteboard so the cosine curve emerges visibly for the whole class.

What to look for

Present students with three scenarios: 1) A box is pushed horizontally across a floor. 2) A weightlifter lifts a barbell straight up. 3) A satellite orbits Earth. Ask students to identify which scenario involves work being done and to briefly explain why or why not, referencing force and displacement.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 02

• Think-Pair-Share
• 45 min · Small Groups

Small Groups Ramp: Gravity Work

Groups construct adjustable ramps with books. Release a cart from height h, measure path length d, and calculate work by gravity as mg h. Vary angles, compare to measured kinetic energy gain, and discuss parallel component.

Analyze how the angle between a constant force and displacement affects the work done.

Facilitation Tip

Before Small Groups Ramp, demonstrate how to zero the spring scale on the incline to avoid systematic error in the force reading.

What to look for

Provide students with a diagram of a force vector and a displacement vector at a 60-degree angle. Ask them to calculate the work done if the force is 50 N and the displacement is 2 m. Include a question asking what would happen to the work done if the angle were 90 degrees.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 03

• Think-Pair-Share
• 25 min · Whole Class

Whole Class Demo: Perpendicular Force

Teacher holds a weight and walks horizontally while students use timers for displacement. Calculate tension work (zero) versus vertical lift work (mgh). Class predicts outcomes, then verifies with whiteboard vectors.

Calculate the work done by gravity or friction over a given displacement.

Facilitation Tip

In Whole Class Demo: Perpendicular Force, have students sketch the force and displacement vectors on mini whiteboards before you release the weight, forcing an immediate prediction.

What to look for

Pose the question: 'Imagine pushing a heavy box across a rough floor. You push horizontally, but the floor exerts a frictional force opposing your motion. Is the work done by you positive or negative? Is the work done by friction positive or negative? Explain your reasoning using the concept of the angle between force and displacement.'

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 04

• Think-Pair-Share
• 30 min · Individual

Individual Calc: Friction Work

Students push blocks across surfaces with known friction coefficients. Measure force to maintain constant speed, compute negative work over distance. Compare to energy lost as heat via thermometer.

Explain why a force perpendicular to displacement does no work.

Facilitation Tip

For Individual Calc: Friction Work, provide a friction coefficient table and remind students to convert mass to kilograms before calculating normal force.

What to look for

Present students with three scenarios: 1) A box is pushed horizontally across a floor. 2) A weightlifter lifts a barbell straight up. 3) A satellite orbits Earth. Ask students to identify which scenario involves work being done and to briefly explain why or why not, referencing force and displacement.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

A few notes on teaching this unit

Start with a quick human demo: have a student push lightly on a wall while standing on a skateboard to feel no displacement, then push on the floor to feel work. This physical anchor keeps the concept grounded. Avoid launching straight into derivations; let students grapple with angle effects first through hands-on pulls, then formalize with the formula. Research shows that linking the cosine term to a measured reduction in force—rather than just memorizing it—improves transfer to new contexts.

By the end of the activities, students will confidently use the cosine term to decide whether a given force does work, and they will quantify that work using force meters, ramps, and simple calculations. You’ll see clear evidence when they sketch vector components or choose the correct sign for friction calculations.

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Watch Out for These Misconceptions

• During Pairs Pull, watch for students who multiply the full force by the distance regardless of angle.

  Have them read the force meter at each angle, then ask why the meter shows less force even though they pull with the same effort; this data shift usually corrects the misconception on the spot.

• During Small Groups Ramp, watch for students who claim zero work occurs because the speed is constant.

  Direct them to tally the applied force and frictional force separately, then ask what each force’s angle is relative to displacement; the imbalance in signs typically clarifies the role of friction.

• During Whole Class Demo: Perpendicular Force, watch for students who predict work because the object visibly moves.

  Pause the demo and have students trace the actual displacement vector on the whiteboard, then draw the force vector; the perpendicular alignment quickly reveals cos90° equals zero.

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Methods used in this brief

• Think-Pair-Share