Fundamental Relationships
- Displacement s, velocity v, and acceleration a are all functions of time.
- Velocity is the rate of change of displacement with respect to time:
v = ds/dt
- Acceleration is the rate of change of velocity with respect to time:
a = dv/dt
Using Calculus
- To move from displacement → velocity → acceleration, use differentiation.
- To move from acceleration → velocity → displacement, use integration.
- Each integration introduces a constant of integration (c), which must be determined from initial conditions.
Velocity–Time Graphs
- Acceleration is the gradient of the velocity–time graph (found using differentiation).
- Displacement is the area under the velocity–time graph (found using integration).
Key Phrases in Questions
- “Starting from rest” → v = 0 when t = 0.
- “Initially” → refers to t = 0.
Integration in Practice
- Integrating acceleration between two times gives the change in velocity over that interval.
- Integrating velocity between two times gives the displacement over that interval.
- Note: Displacement can differ from distance travelled.
- To find total distance, calculate areas above and below the x‑axis separately.
Important Reminders
- Watch for scalar vs vector keywords:
- Scalars: distance, speed, magnitude.
- Vectors: displacement, velocity, acceleration.
- Sketching a velocity–time graph is always helpful:
- It shows when the object is stationary.
- It helps in calculating total distance travelled clearly.
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