Measuring Force

Students learn best about force when they feel it and see it in action, not just when they read about it. Designing hands-on experiments with spring scales and everyday objects helps students connect abstract concepts like Newtons to the tangible world of pushes and pulls they experience every day.

• 3rd Year
• Exploring Our World: Scientific Inquiry and Discovery
• 4 activities
• 20 min–50 min

Learning Objectives

1. Compare the magnitude of forces required to move objects of different masses using a spring scale.
2. Explain how the extension of a spring in a spring scale relates to the force applied.
3. Design a fair test to investigate the effect of friction on the force needed to move an object.
4. Evaluate the importance of using consistent units (Newtons) when measuring and recording force data.

Problem-Based Learning

⏱ 30 min·Pairs

Pairs: Object Lift Comparison

Pairs choose five classroom objects of different masses, such as erasers and books. Attach each to a spring scale and pull upward steadily at eye level, recording the newton reading. Compare results and discuss why heavier items show higher forces. Graph data to spot trends.

Prepare & details

Explain how a spring scale measures the strength of a force.

Facilitation Tip: Before pairs begin Object Lift Comparison, circulate to ensure students hold the spring scale vertically and avoid side pulls, which skew readings.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

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

Problem-Based Learning

⏱ 45 min·Small Groups

Small Groups: Surface Drag Stations

Set up stations with surfaces like table tops, sandpaper, and fabric. Groups drag a constant object using a spring scale, measure pull force needed to start motion, and rotate stations. Record averages after three trials per surface. Share findings in a class chart.

Prepare & details

Design an experiment to compare the force needed to move different objects.

Facilitation Tip: At each Surface Drag Station, remind groups to keep the spring scale at a steady pace and record times to standardize pulling speed across trials.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

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

Problem-Based Learning

⏱ 50 min·Whole Class

Whole Class: Fair Test Design Challenge

Brainstorm variables affecting force, like object shape. Class votes on one, such as pulling blocks versus balls. Demonstrate consistent technique with spring scale. Students predict, test in pairs, and report data to evaluate test fairness.

Prepare & details

Evaluate the importance of consistent measurement in scientific investigations.

Facilitation Tip: During the Fair Test Design Challenge, ask guiding questions like 'What will stay the same?' to help students isolate the variable they are testing.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

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

Problem-Based Learning

⏱ 20 min·Individual

Individual: Force Diary

Each student measures forces for personal pushes or pulls, like opening doors or stretching rubber bands with a scale. Log readings with sketches. Compile into a class display to compare everyday forces.

Prepare & details

Explain how a spring scale measures the strength of a force.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

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

Teaching This Topic

Teach this topic by letting students experience the challenges of measuring force firsthand before explaining theory. Avoid starting with definitions—instead, let them struggle with inconsistent readings due to friction or speed, then use those moments to introduce precise terms like 'Newton' and 'fair test.' Research shows these 'aha' moments stick better than direct instruction alone.

What to Expect

By the end of the activities, students should confidently use spring scales to measure force, explain how friction and mass affect force, and design fair tests to compare different scenarios. Success looks like clear data collection, thoughtful analysis, and accurate explanations tied to their observations.

Watch Out for These Misconceptions

Common Misconception

During the Object Lift Comparison activity, watch for students assuming that doubling the mass means doubling the force.

What to Teach Instead

After students measure the forces, have them compare the actual Newtons recorded and ask, 'Does doubling mass always mean double the force?' Use their data to guide a discussion on the role of friction and surface.

Common Misconception

During the Surface Drag Stations activity, watch for students thinking the spring scale measures weight rather than applied force.

What to Teach Instead

Ask pairs to lift an object vertically using the scale, then drag it horizontally. Have them compare the readings and explain why the numbers differ, reinforcing that the scale measures any push or pull.

Common Misconception

During the Fair Test Design Challenge, watch for students ignoring the impact of pulling speed on force readings.

What to Teach Instead

After trials, ask groups to describe how their pulling speed varied and how it might have affected results. Guide them to adjust their methods for more consistent trials in future tests.

Assessment Ideas

Exit Ticket

After the Object Lift Comparison activity, provide students with a spring scale and two objects of different masses. Ask them to measure the force needed to lift each object steadily and record the measurement in Newtons. On the back, have them write one sentence explaining which object required more force and why.

Discussion Prompt

During the Surface Drag Stations activity, present students with a scenario: 'Imagine you are designing a ramp for a toy car. What factors would affect the force needed to push the car up the ramp?' Guide them to discuss friction and the car's weight, prompting them to consider how they would measure these forces in their stations.

Quick Check

After the Fair Test Design Challenge, show students a diagram of a spring scale with a weight attached. Ask: 'If the spring stretches further, does this mean the force is larger or smaller? Explain your answer using the term 'Newton'.'

Extensions & Scaffolding

• Challenge early finishers to design a new ramp surface using classroom materials and predict how the force needed to move a toy car will change.
• For students struggling to steady their pulls, provide a metronome app set to a slow, steady beat to help them maintain consistent speed.
• Deeper exploration: Have students research how engineers use force measurements in designing playground equipment or vehicle safety features, then present findings to the class.

Key Vocabulary

Force	A push or a pull that can cause an object to change its motion or shape.
Newton (N)	The standard unit for measuring force. One Newton is the force required to accelerate a mass of one kilogram at a rate of one meter per second squared.
Spring Scale	A device that measures force by measuring how much a spring stretches or compresses.
Friction	A force that opposes motion when two surfaces rub against each other.