Projectile Motion

Overview

Projectile motion looks two-dimensional, but the calculation becomes manageable when you split it into horizontal and vertical components. Time is the link between the two directions.

What You Need to Know

• In the usual AS model, horizontal velocity is constant because horizontal acceleration is zero.
• Vertical motion has uniform acceleration due to gravity.
• Resolve the initial velocity before using SUVAT.
• The horizontal and vertical motions happen over the same time interval.
• Air resistance is ignored unless the question says otherwise.

How to Work Through It

1. Draw the path and mark the initial velocity components.
2. Write separate horizontal and vertical information columns.
3. Use the vertical motion to find time when needed.
4. Use that same time in the horizontal motion to find range or displacement.

Check Your Understanding

• Why is there no horizontal acceleration in the ideal projectile model?
• Which direction usually uses SUVAT, and why?
• What connects the horizontal and vertical calculations?
• How does the velocity change during the flight?

Common Mistakes

• Using the full launch speed in a horizontal equation instead of the horizontal component.
• Forgetting that the vertical velocity changes while the horizontal velocity stays constant.
• Assuming the time to rise always equals the time to fall, even when launch and landing heights differ.
• Mixing horizontal and vertical quantities in one SUVAT line.

Next Steps

• Practise setting up the horizontal and vertical columns before attempting the algebra.
• Bring unresolved questions to the practice lesson, where the focus is method fluency.