Physics · 9th Grade

Active learning ideas

Projectile Motion: Horizontal Launch

Active learning works for projectile motion because students often hold intuitive but incorrect ideas about how objects move through the air. By physically launching marbles and carefully observing their paths, students experience the independence of horizontal and vertical motion firsthand, replacing abstract equations with concrete evidence.

• Common Core State Standards
• HS-PS2-1
• CCSS.MATH.CONTENT.HSF.LE.A.1

• 20–50 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Inquiry Circle
• 50 min · Small Groups

Inquiry Circle: Marble Launcher Landing Spot

Groups fire a marble horizontally from a known height using a ramp. They measure the launch height and use slow-motion video to estimate initial horizontal velocity, then calculate the predicted landing distance. Groups mark the predicted spot with tape and fire to test their prediction.

How does the horizontal velocity of a projectile change throughout its flight?

Facilitation Tip

During Collaborative Investigation: Marble Launcher Landing Spot, circulate and ask each group to justify their predicted landing spot using both the time of flight calculation and the horizontal velocity measurement.

What to look for

Provide students with a diagram of a ball rolling off a table at a known speed. Ask them to write down the initial horizontal velocity and the initial vertical velocity. Then, ask them to identify which component of motion (horizontal or vertical) will be affected by gravity.

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

Activity 02

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: The Time Link

Pairs work through a two-step problem where they must first use the vertical free-fall equation to find time of flight, then use that time in the horizontal equation to find range. Each pair explains the role of the shared time variable to another pair before the class compares solutions.

Predict the landing spot of a horizontally launched projectile given its initial conditions.

Facilitation Tip

During Think-Pair-Share: The Time Link, listen for pairs who recognize that the ball dropped straight down and the horizontally launched ball hit the ground at the same time, then invite them to share that observation with the class.

What to look for

Present students with a scenario: 'A ball is launched horizontally from a height of 1.5 meters with an initial speed of 5 m/s. Calculate its time of flight and horizontal range.' Students write their answers and show their work.

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

Activity 03

• Gallery Walk
• 30 min · Small Groups

Gallery Walk: Trajectory Diagram Annotation

Posted diagrams show horizontally launched projectiles at different heights and speeds. Groups annotate each diagram with horizontal velocity vectors, vertical velocity vectors at multiple time intervals, and the net velocity direction at each point, then rotate to compare annotations with the previous group.

Explain why the time of flight for a horizontally launched projectile depends only on its vertical drop.

Facilitation Tip

During Gallery Walk: Trajectory Diagram Annotation, provide a checklist of elements to include (initial velocities, acceleration vector, time intervals) so students know exactly what to look for as they move between stations.

What to look for

Pose the question: 'If you double the horizontal launch speed of a projectile, how does its time of flight change? How does its range change? Explain your reasoning using the concepts of independent motion.'

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

A few notes on teaching this unit

Teach this topic by starting with a dramatic demonstration: drop a ball and launch another horizontally from the same height at the same moment. The audible ‘thud’ of both hitting the ground together immediately challenges the misconception that horizontal speed affects flight time. Avoid rushing to equations before students see the phenomenon. Research suggests students learn best when they first observe, then measure, and finally model the motion with graphs and calculations.

Successful learning looks like students explaining why horizontal velocity doesn’t affect time of flight, accurately predicting landing spots using calculations, and annotating trajectory diagrams with clear labels for velocity components and acceleration arrows. They should connect mathematical predictions to physical outcomes during hands-on experiments.

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Watch Out for These Misconceptions

• During Collaborative Investigation: Marble Launcher Landing Spot, watch for students who argue that a faster marble will fly longer because it travels farther.

  Use the marble launcher setup to show that marbles launched from the same height, regardless of horizontal speed, hit the ground at the same time. Have students measure the time of flight for different speeds using a stopwatch or motion sensor.

• During Gallery Walk: Trajectory Diagram Annotation, watch for students who draw curved or decreasing horizontal velocity vectors.

  Have students compare their diagrams to the marble’s actual path captured on video or a slow-motion animation. Ask them to redraw the horizontal velocity vectors as straight, equally spaced arrows to match the constant speed.

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Methods used in this brief

• Inquiry Circle
• Think-Pair-Share
• Gallery Walk