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QLDPhysicsQuick questions
Unit 2: Linear motion and waves
Quick questions on Displacement, velocity and acceleration (QCE Physics Unit 2)
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is position?Show answer
The location of an object relative to a reference point, given as a coordinate (often $x$ or $\vec{r}$). Vector.
What is distance?Show answer
The total length of the path travelled. Scalar.
What is displacement?Show answer
The change in position from start to finish, $\Delta \vec{r} = \vec{r}_f - \vec{r}_i$. Vector. Independent of path.
What is speed?Show answer
Distance per unit time. Scalar.
What is velocity?Show answer
Rate of change of displacement. Vector.
What is acceleration?Show answer
Rate of change of velocity. Vector.
What is treating speed and velocity as identical?Show answer
A car driving in a circle at constant speed has zero average velocity over a full lap (start position equals end position).
What is forgetting direction on vectors?Show answer
QCAA penalises numerical answers for displacement, velocity and acceleration that omit direction.
What is confusing slowing down with negative acceleration?Show answer
A negative acceleration only means slowing down if the velocity is positive. If velocity is also negative, the object is speeding up.
What is using an average value instantaneously?Show answer
Average velocity over $10$ s is not the velocity at $t = 5$ s unless the motion is uniformly accelerated.