Quick questions on Motion and kinematics: suvat, graphs and projectiles - Edexcel A-Level Physics

Reading graphs both ways (gradient and area) is a core skill. A negative gradient on a displacement-time graph means motion in the negative direction; an area below the axis on a velocity-time graph counts as negative displacement.

List the known quantities, choose the equation that contains your three knowns and the unknown, and solve. These apply only when the acceleration is constant; for free fall near the ground, $a = g \approx 9.81$ m per second squared downward.

A projectile experiences a constant downward acceleration $g$ and no horizontal force (ignoring air resistance). The horizontal and vertical motions are independent: horizontally the velocity is constant ($x = u_x t$); vertically the suvat equations apply with $a = g$. Combining them gives a parabolic trajectory. For a projectile launched at angle $\theta$ with speed $u$, resolve into $u_x = u\cos\theta$ and $u_y = u\sin\theta$, then treat each direction separately.

State what the area under a velocity-time graph represents. [1 mark]

A stone is dropped from rest and falls for $3.0$ s. Find its speed on impact. Take $g = 9.81$ m per second squared.

Explain why the horizontal velocity of a projectile is constant (ignoring air resistance). [2 marks]