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VICPhysicsQuick questions
Unit 3: How do fields explain motion and electricity?
Quick questions on Projectile motion in two dimensions: VCE Physics Unit 3
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 resolving the initial velocity?Show answer
If a projectile is launched with speed $v_0$ at angle $\theta$ above the horizontal:
What is horizontal motion?Show answer
No horizontal force acts (air resistance ignored), so horizontal velocity is constant.
What is vertical motion?Show answer
The only acceleration is gravity, $a_y = -g = -9.8$ m/s squared (taking up as positive). Use SUVAT:
What is key features of the trajectory?Show answer
The path is a parabola. At maximum height $v_y = 0$, so $h_{\max} = \frac{v_{0y}^2}{2g}$.
What is air resistance (qualitative)?Show answer
Air resistance (drag) acts opposite to the velocity vector at every instant and increases with speed (roughly $F_{drag} \propto v^2$). Its effects on a projectile:
What is mixing horizontal and vertical equations?Show answer
Horizontal velocity is constant (no drag). Vertical velocity changes by $9.8$ m/s each second. Two separate columns of working.
What is forgetting the sign of $g$?Show answer
Pick a positive direction (up or down) and apply it consistently to $v_{0y}$, $a_y$ and $y$.
What is using the launch speed instead of a component?Show answer
$v_0 = 25$ m/s at $40°$ does not mean horizontal velocity is $25$ m/s. Resolve first.
What is treating a horizontally thrown object as having $v_{0y} = v_0$?Show answer
If a stone is thrown horizontally off a cliff, $v_{0y} = 0$.
What is treating air resistance as a constant force?Show answer
Drag depends on speed; expect a qualitative description, not a numerical one.