HSC Physics — Module 1
Projectile Motion — Flashcards & Quiz
Projectile motion is a key topic in HSC Physics Module 1, where an object moves under gravity with no other forces acting (ignoring air resistance). The fundamental principle is that horizontal and vertical motions are independent — horizontal velocity stays constant while vertical velocity changes at 9.8 m/s². You need to resolve initial velocities into components, calculate time of flight, range, and maximum height. Exam questions frequently require multi-step calculations combining kinematics equations with vector decomposition.
Sample Flashcards
Q1: Describe projectile motion and its two components.
Projectile motion is the motion of an object launched into the air under gravity only. It has two independent components: horizontal (constant velocity, a_x = 0) and vertical (constant acceleration, a_y = g = 9.8 m/s² downward). The path is a parabola.
Q2: How do you calculate the range and maximum height of a projectile?
Time of flight: t = 2u sinθ/g. Maximum height: H = u²sin²θ/(2g). Range: R = u²sin2θ/g. Maximum range occurs at θ = 45°. These formulas assume launch and landing are at the same height.
Q3: Why does air resistance affect projectile motion?
Air resistance (drag) opposes motion in both horizontal and vertical directions. Horizontally, it decelerates the projectile (v_x is no longer constant). Vertically, it reduces both the maximum height and time of flight. The trajectory becomes asymmetric — steeper on descent.
Q4: What happens at the peak of a projectile's trajectory?
At the peak: vertical velocity v_y = 0 (momentarily stationary in the vertical direction). Horizontal velocity v_x remains unchanged (no horizontal acceleration). The object is still moving horizontally. Acceleration = g = 9.8 m/s² downward (never zero during flight).
Sample Quiz Questions
Q1: The horizontal velocity of a projectile remains constant throughout its flight (ignoring air resistance).
Answer: TRUE
With no air resistance, there is no horizontal force, so horizontal acceleration = 0. By Newton's first law, horizontal velocity remains constant throughout the flight.
Q2: The acceleration of a projectile is zero at the highest point of its trajectory.
Answer: FALSE
Acceleration due to gravity is CONSTANT at 9.8 m/s² downward throughout the entire flight, including at the peak. Only the vertical VELOCITY is zero at the highest point, not the acceleration.
Q3: A ball thrown horizontally from a cliff takes longer to reach the ground than one dropped vertically from the same height.
Answer: FALSE
Both take the same time. Horizontal and vertical motions are independent. The horizontal velocity doesn't affect the vertical fall time, which depends only on height and g.
Last updated: March 2026 · 4 flashcards · 4 quiz questions