Quick questions on Projectile motion (QCE Physics Unit 3)

No horizontal force acts (air resistance is ignored), so the horizontal velocity is constant.

Expect either a launch-angle table to interpret (range vs angle data, often missing one value), or a single trajectory with annotated heights and asked to extract launch speed and landing time. Marker traps focus on candidates who plug the resultant speed in place of a component or forget to use $r = R_E + h$ on the vertical axis when a height above the launch is involved.

The standard projectile IA2 measures range as a function of launch angle for a fixed launch speed (small projectile launcher or a ball-bearing on a ramp). A strong report linearises by plotting $R$ against $\sin(2\theta)$ (slope $= v_0^2 / g$), reports a $v_0$ that agrees with a direct measurement, and discusses air-resistance and release-height systematic effects in the evaluation. The IA2 criteria reward the design justification, the data, and the evaluation in that order.

State the assumption made when analysing projectile motion in QCAA Unit 3. [2 marks]

A ball is thrown at $20 \text{ m s}^{-1}$ at $30^\circ$ above horizontal. Calculate the time aloft and the range, $g = 9.8 \text{ m s}^{-2}$. [3 marks]

A bagasse conveyor discharges horizontally at $4.0 \text{ m s}^{-1}$ from $3.0 \text{ m}$ above the hopper. (a) Calculate the time to fall and the range. (b) Determine the speed and angle of impact below horizontal.