Forces: Pushes and Pulls

Active learning helps students grasp forces because motion and interaction are visible and tangible. When students manipulate objects and measure outcomes, abstract concepts like balanced and unbalanced forces become concrete. Collaborative experiments also reveal misconceptions through direct observation and discussion.

• 6th Year
• Advanced Chemical Principles and Molecular Dynamics
• 4 activities
• 20 min–45 min

Learning Objectives

1. Classify forces as either contact or non-contact forces based on their interaction with objects.
2. Compare the effect of balanced and unbalanced forces on the motion of an object.
3. Explain how gravity causes objects to accelerate towards the Earth.
4. Demonstrate the relationship between applied force and changes in motion using a simple experiment.
5. Analyze the role of friction in opposing motion between surfaces.

⏱ 45 min·Small Groups

Ramps and Rollers: Friction Investigation

Provide ramps at three angles and surfaces: smooth wood, carpet, sandpaper. Students roll marbles, measure distances, and time descents. They predict and test how friction changes speed, recording in tables for class comparison.

Prepare & details

What is a force?

Facilitation Tip: During Ramps and Rollers, provide different surfaces for the rollers to emphasize how texture changes friction, and ask students to predict which will slow down fastest before testing.

⏱ 30 min·Pairs

Push-Pull Tug-of-War

Mark a line on the floor; pairs pull ropes with spring scales to measure force. Switch roles and add weights to one side. Groups graph force versus motion outcome and discuss balanced versus unbalanced forces.

Prepare & details

How do pushes and pulls make things move?

Facilitation Tip: For Push-Pull Tug-of-War, have students anchor their scale readings on a whiteboard to compare forces directly and discuss why equal readings mean balanced forces.

⏱ 35 min·Small Groups

Gravity Drop Challenge

Drop balls of same size but different materials from heights; measure fall times with stopwatches. Students vary heights and predict patterns, then create posters explaining gravity's constant pull.

Prepare & details

What is gravity and how does it affect us?

Facilitation Tip: In Gravity Drop Challenge, use a metronome or timer to standardize drop intervals so students can focus on consistent data collection rather than guessing timing.

⏱ 20 min·Whole Class

Whole Class Force Chain

Students stand in a circle holding strings tied to a central object. On cue, they push or pull gently; observe chain reactions. Discuss force transmission and net force effects.

Prepare & details

What is a force?

Facilitation Tip: During Whole Class Force Chain, assign roles to students so each can feel the direction and strength of the force they apply to the next person in line.

Teaching This Topic

Teach this topic through guided inquiry where students make predictions, test ideas, and revise models based on evidence. Avoid explaining forces in isolation; instead, let students experience confusion and resolve it through structured exploration. Research shows hands-on measurement of forces builds lasting understanding, while only discussing forces through diagrams often leads to persistent misconceptions.

What to Expect

Students will confidently identify pushes and pulls as forces that change motion, describe friction and gravity as opposing forces, and explain how balanced or unbalanced forces determine an object's movement. They will use evidence from activities to support their explanations and adjust their understanding based on data.

Watch Out for These Misconceptions

Common Misconception

During Push-Pull Tug-of-War, watch for students who label only the 'pull' end as applying force while ignoring the 'push' end.

What to Teach Instead

Have students record both sides of the rope's tension using spring scales, then ask them to explain why the scales read the same when the rope is stationary, reinforcing that pulls are just as valid as pushes.

Common Misconception

During Gravity Drop Challenge, watch for students who claim heavier objects fall faster because they experience stronger gravity.

What to Teach Instead

After timing falls, ask groups to plot their data and compare the acceleration rates of light and heavy objects. Then, use a fan to show how air resistance affects lighter objects more, linking friction to their observations.

Common Misconception

During Ramps and Rollers, watch for students who believe motion continues indefinitely once started if no force is applied.

What to Teach Instead

Extend the ramp with a flat surface and ask students to measure how long the roller travels after leaving the ramp. Discuss how friction slows the roller, and have them calculate the deceleration rate from their data.

Assessment Ideas

Exit Ticket

After Ramps and Rollers, provide students with a diagram of a rolling ball on a flat surface slowing to a stop. Ask them to label the forces acting on the ball and explain whether they are balanced or unbalanced, using their experiment as evidence.

Quick Check

During Push-Pull Tug-of-War, ask students to write down the force they applied and the opposing force they felt, then share with a partner before discussing how balanced and unbalanced forces feel different.

Discussion Prompt

After Gravity Drop Challenge, pose the question: 'Why did the feather and ball sometimes hit the ground at the same time in your tests?' Guide students to discuss gravity, air resistance, and how unbalanced forces cause acceleration, referencing their data tables.

Extensions & Scaffolding

• Challenge: After Ramps and Rollers, have students design a ramp with the least friction by testing materials and angles, then present their optimal setup to the class.
• Scaffolding: For students struggling with Gravity Drop Challenge, provide pre-labeled graphs with empty data tables so they can focus on recording and interpreting results rather than setup.
• Deeper exploration: During Whole Class Force Chain, add a spring scale to measure the force at different points in the chain and discuss how force magnitude changes along the line of action.

Key Vocabulary

Force	A push or a pull that can cause an object to move, stop moving, or change direction.
Gravity	A non-contact force that attracts any two objects with mass. On Earth, it pulls objects towards the planet's center.
Friction	A contact force that opposes motion when two surfaces rub against each other.
Balanced Forces	When two or more forces acting on an object are equal in strength and opposite in direction, resulting in no change in motion.
Unbalanced Forces	When forces acting on an object are not equal in strength or opposite in direction, causing a change in the object's motion (acceleration).