Physics · 10th Grade

Active learning ideas

Newton's Second Law: F=ma

Active learning helps students grasp Newton’s Third Law because the abstract concept of action-reaction pairs becomes concrete when they physically feel forces on different objects. When students move and measure forces themselves, they directly experience why balanced forces don’t cancel motion.

• Common Core State Standards
• STD.HS-PS2-1
• CCSS.HS-CED.A.4

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

Activity 01

• Inquiry Circle
• 30 min · Pairs

Inquiry Circle: Skateboard Push-Off

Two students stand on skateboards and push against each other. They observe that both move backward, regardless of who did the 'pushing.' They then repeat with one student holding a heavy weight to see how mass affects the resulting acceleration.

How does an increase in payload affect a rocket's launch acceleration?

Facilitation Tip

During the Skateboard Push-Off, stand close to students to ensure safety as they push off the ground and roll backward.

What to look for

Present students with three scenarios: 1) A 10 kg box pushed with 20 N. 2) A 20 kg box pushed with 20 N. 3) A 10 kg box pushed with 40 N. Ask students to rank the resulting accelerations from least to greatest and briefly justify their ranking using F=ma.

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

Activity 02

• Peer Teaching
• 45 min · Small Groups

Peer Teaching: Balloon Rocket Engineering

Groups design balloon rockets on a string. They must explain to the class how the air pushing out the back (action) results in the balloon moving forward (reaction) and identify the two objects involved in the force pair.

Why do heavy trucks require more powerful braking systems than small cars?

Facilitation Tip

For the Balloon Rocket Engineering activity, assign roles clearly so each student has a part in building, measuring, and recording results.

What to look for

Provide students with a diagram of a car being towed by a rope. Include the mass of the car and the tension in the rope. Ask students to calculate the car's acceleration and explain in one sentence what would happen to the acceleration if the car's mass were doubled, assuming the same rope tension.

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

Activity 03

• Think-Pair-Share
• 25 min · Pairs

Think-Pair-Share: The Horse and Cart Paradox

Present the riddle: 'If the cart pulls back on the horse as hard as the horse pulls on the cart, how can they move?' Students discuss in pairs, focusing on the forces acting on the ground versus the forces acting on the cart.

How can we calculate the net force on an object moving through a fluid?

Facilitation Tip

In the Think-Pair-Share for The Horse and Cart Paradox, remind students to use free-body diagrams to visualize forces on each object separately.

What to look for

Pose the question: 'Imagine you are pushing a shopping cart. If you push with the same force, why does the cart accelerate less when it is full compared to when it is empty?' Guide students to use the terms mass, net force, and acceleration in their explanations.

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

A few notes on teaching this unit

Experienced teachers approach this topic by first letting students feel the forces themselves before formalizing the concept with equations. Avoid starting with the formula F=ma; instead, use real-world examples where students observe unbalanced forces causing motion despite equal and opposite pairs. Research shows students grasp Newton’s Third Law better when they analyze motion first, then connect it to force pairs.

Successful learning looks like students confidently explaining that forces in an action-reaction pair act on different objects and do not cancel each other out. They should be able to predict motion outcomes based on mass and force differences after these activities.

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Watch Out for These Misconceptions

• During the Skateboard Push-Off activity, watch for students who say forces cancel out when they feel themselves roll backward.

  Use force sensors to display two identical force-time graphs: one for the foot pushing the ground and one for the ground pushing the foot. Ask students to explain how the motion occurs if the forces are equal.

• During the Balloon Rocket Engineering activity, watch for students who assume the bigger balloon exerts more force.

  Have students measure the thrust force of each balloon using a spring scale and compare it to the resulting acceleration of the rocket. Discuss why the smaller balloon might accelerate the rocket more if it has less mass.

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Methods used in this brief

• Inquiry Circle
• Peer Teaching
• Think-Pair-Share