At time ttt seconds a particle, PPP, has position vector r\mathbf{r}r metres, with respect to a fixed origin, such that
r=(t3−4t2)i+(12t−t2)j \mathbf{r} = (t^3 - 4t^2)\mathbf{i} + (12t - t^2)\mathbf{j} r=(t3−4t2)i+(12t−t2)jFind the exact speed of PPP when t=3t = 3t=3.
A student claims that the magnitude of acceleration of PPP will never be zero. Determine whether the student's claim is correct. Fully justify your answer.
260 exam-style questions on OCR A Level Maths 3.2 Kinematics, covering 3.2.1 Language of kinematics, 3.2.2 Graphs in kinematics, 3.2.3 Displacement-time and velocity-time graphs, 3.2.4 Constant acceleration formulae, 3.2.5 Constant acceleration in two dimensions (A-level only), 3.2.6 Non-uniform acceleration in one dimension (A-level only), 3.2.7 Non-uniform acceleration in two dimensions (A-level only), 3.2.8 Motion under gravity using vectors (A-level only), and 3.2.9 Projectiles (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.