VCE Physics — Unit 3 AOS 1
Projectile Motion — Flashcards & Quiz
Projectile motion combines constant horizontal velocity with constant vertical acceleration under gravity, and VCE Physics Unit 3 AOS 1 expects you to resolve the launch velocity into components, apply kinematic equations to each direction independently, and solve for range, maximum height or time of flight. Air resistance is ignored unless specifically stated.
Key Points
- Horizontal motion: constant velocity uₓ = u cosθ (no air resistance, no acceleration).
- Vertical motion: constant downward acceleration g = 9.8 m s⁻²; initial velocity uᵧ = u sinθ.
- Time of flight on level ground: t = 2u sinθ / g.
- Range: R = u² sin(2θ) / g; maximum at θ = 45°.
- Maximum height: H = (u sinθ)² / (2g); reached when vertical velocity = 0.
- At the peak, velocity is purely horizontal — vertical component has momentarily become zero.
Common Mistakes to Avoid
- Mixing up sin and cos — for θ from horizontal, horizontal component is u cosθ, vertical is u sinθ.
- Adding horizontal and vertical velocities like scalars — they are perpendicular components.
- Claiming horizontal velocity decreases during flight — it is constant (ignoring air resistance).
- Applying the range formula to an uneven landing surface — it only works when launch and landing heights are equal.
- Forgetting signs: if up is positive, g = –9.8 m s⁻².
Exam Strategy
VCAA Unit 3 AOS 1 projectile questions give you a launch scenario and ask for time, range, maximum height, or velocity at a specific moment. Method: (1) resolve u into u cosθ (horizontal) and u sinθ (vertical), (2) apply SUVAT to each direction independently, (3) use time as the bridge, (4) state assumptions such as no air resistance and level ground. Diagrams of the trajectory with component arrows add clarity.
Sample Flashcards
Q1: What are the two key principles of projectile motion?
1) Horizontal and vertical motions are independent. 2) Horizontal velocity is constant (no horizontal acceleration); vertical motion has constant acceleration (g = 9.8 m s⁻² downward). Treat the two components separately, then combine to find trajectory.
Q2: What equations govern the horizontal and vertical motion of a projectile?
Horizontal: x = v_x t (constant velocity). Vertical: v_y = u_y − gt, y = u_y t − ½gt², v_y² = u_y² − 2gy (constant acceleration −g). Combine equations to find range, maximum height, and time of flight.
Q3: What is the trajectory shape of a projectile and what is the range formula?
The trajectory is a parabola (assuming no air resistance). For launch and landing at the same height, range R = (v₀² sin 2θ)/g. Maximum range occurs at θ = 45°. Time of flight: t = (2v₀ sin θ)/g.
Q4: How does air resistance affect projectile motion?
Air resistance opposes motion, reducing both horizontal and vertical components of velocity. The trajectory is no longer symmetric — range is reduced, maximum height is reduced, time of flight is reduced, and the descent is steeper than the ascent. Terminal velocity may be reached.
Q5: What are the horizontal and vertical velocity components at the peak of a projectile's flight?
At maximum height, the vertical velocity component is zero (v_y = 0) while the horizontal component remains constant (v_x = v₀ cos θ). The projectile momentarily stops moving vertically but continues moving horizontally.
Sample Quiz Questions
Q1: Horizontal and vertical motions of a projectile are independent of each other.
Answer: TRUE
Horizontal motion (constant velocity) and vertical motion (constant acceleration −g) can be analysed separately and do not affect each other.
Q2: A projectile launched horizontally has zero initial vertical velocity.
Answer: TRUE
When launched horizontally, u_y = 0. Vertical velocity increases due to gravity as the projectile falls.
Q3: The maximum range for a projectile is achieved at a launch angle of 60°.
Answer: FALSE
Maximum range (for launch and landing at the same height) occurs at θ = 45°, not 60°. R = (v₀² sin 2θ)/g is maximum when sin 2θ = 1.
Revision Tip
Projectile decomposition is the one pattern every VCE exam tests — drill a Revizi deck with 8+ scenarios (horizontal launch, angled launch, from a cliff, landing at different height) to make the method automatic.
Related Concepts
Last updated: March 2026 · 5 flashcards · 6 quiz questions