Weight and perpendicular motion components

Repair the common break

Common misconception: Gravity changes horizontal velocity in ideal projectile motion.

Correct model: Resolve the motion: horizontal velocity is uniform while vertical motion has uniform gravitational acceleration when air resistance is neglected.

Worked transfer

For a projectile launched at 20 m s⁻¹ at 30°, ux = 17.3 m s⁻¹ stays constant while uy begins at 10.0 m s⁻¹ and changes as vy = 10.0 − gt. The components share time but have different accelerations.

Guided practice

Explain why “Gravity changes horizontal velocity in ideal projectile motion.” fails. Then construct one example that correctly applies weight and perpendicular motion components.

Independent practice

A ball leaves a cliff horizontally at 12 m s⁻¹ and lands 1.5 s later. Find its horizontal displacement and vertical velocity just before impact.

Return to the recorded repair plan when the explanation and application are secure enough to re-test.