Defining momentum, the law of conservation of linear momentum, and applying it to collisions and explosions along a straight line.
5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
A cricket ball and a bowling ball can be moving at the same speed, but you would never choose to catch the bowling ball. Momentum measures the difference.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Collide two trolleys. Compare the total momentum before and after.
Copy these into your notebook in your own words — that is how they stick.
p = mv; unit kg m/s = N s; vector.
Total momentum before = total momentum after (no external resultant force).
Choose one direction as positive; opposite is negative.
m₁u₁ + m₂u₂ = (m₁ + m₂)v.
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂.
Starting from rest, total momentum = 0 so the parts move in opposite directions.
Ft = Δp; longer time gives smaller force.
Momentum is conserved; kinetic energy is not always conserved.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Physics Arcade.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (15 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [15 marks]
A trolley A of mass 2.0 kg moves at 3.0 m/s towards a stationary trolley B of mass 1.0 kg. After the collision they stick together.
(a) (a) Define linear momentum and state its unit. [2]
(b) (b) Calculate the total momentum before the collision. [3]
(c) (c) State the principle you would use to find the velocity after the collision. [1]
(d) (d) Calculate the velocity of the trolleys after the collision. [3]
(e) (e) Calculate the kinetic energy before and after, and comment on the result. [4]
(f) (f) Explain, using momentum, why a gun recoils when it fires a bullet. [2]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.