ACT SSC Physics — Unit 1
Kinematics — Flashcards & Quiz
Kinematics describes motion without considering the forces that cause it, using displacement, velocity and acceleration. ACT SSC Physics Year 12 Unit 1 expects you to apply the five SUVAT equations for uniformly accelerated motion, interpret displacement-time and velocity-time graphs, and handle projectile motion as a special case.
Key Points
- Displacement (vector) is different from distance (scalar); velocity (vector) is different from speed (scalar).
- Acceleration is the rate of change of velocity, not speed. Deceleration is acceleration opposite to motion.
- SUVAT equations (for constant acceleration): v = u + at, s = ut + ½at², v² = u² + 2as, s = ½(u+v)t.
- Displacement-time graph: gradient = velocity; curved line = non-uniform velocity.
- Velocity-time graph: gradient = acceleration; area under graph = displacement.
- Free fall: a = –9.8 m/s² (with up positive); SUVAT equations apply directly.
Common Mistakes to Avoid
- Confusing distance (scalar, total path) with displacement (vector, straight line from start).
- Applying SUVAT to non-uniform acceleration — it only works when a is constant.
- Forgetting sign conventions — if up is positive, g = –9.8 m/s².
- Reading displacement-time graphs as if they were velocity-time graphs (or vice versa).
- Using the wrong SUVAT equation — pick the one that uses your three knowns and gives the unknown.
Exam Strategy
BSSS Unit 1 kinematics questions ask you to solve motion problems using SUVAT or interpret graphs. Method: (1) list knowns (u, v, a, s, t), (2) identify the unknown, (3) choose the SUVAT equation linking them, (4) solve symbolically before substituting numbers, (5) check units and sign.
Sample Flashcards
Q1: What is the difference between distance and displacement?
Distance is the total length of the path travelled (scalar). Displacement is the straight-line distance from start to finish in a specified direction (vector).
Q2: Define velocity and distinguish it from speed.
Velocity is the rate of change of displacement (vector, m/s). Speed is the rate of change of distance (scalar, m/s). Average velocity = Δs / Δt.
Q3: Define acceleration and state its SI unit.
Acceleration is the rate of change of velocity: a = Δv / Δt. SI unit: m s⁻². An object accelerates when its speed or direction (or both) changes.
Q4: List the four SUVAT equations of uniformly accelerated motion.
1) v = u + at 2) s = ut + ½at² 3) v² = u² + 2as 4) s = ½(u + v)t. Where: s = displacement, u = initial velocity, v = final velocity, a = acceleration, t = time.
Q5: How do you find displacement from a velocity–time graph?
Displacement equals the area under a velocity–time graph. Areas above the time axis are positive displacement; areas below are negative.
Sample Quiz Questions
Q1: Displacement is a scalar quantity.
Answer: FALSE
Displacement is a vector — it has both magnitude and direction. Distance is the scalar equivalent.
Q2: An object moving in a circle at constant speed has zero acceleration.
Answer: FALSE
The object has centripetal acceleration because its direction is constantly changing, even though speed is constant.
Q3: The gradient of a displacement–time graph gives velocity.
Answer: TRUE
Velocity = Δs/Δt, which is the gradient (slope) of a displacement–time graph.
Revision Tip
SUVAT equation choice is pattern recognition — drill a Revizi deck with 10+ scenarios requiring different equations for fluency.
Last updated: March 2026 · 5 flashcards · 4 quiz questions