Archimedes’ principle, upthrust and apparent weight, predicting whether an object floats or sinks, and applications to ships, submarines and balloons.
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 steel ship floats yet a steel pin sinks. Archimedes’ principle explains both, and a few simple calculations decide which will happen.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Change the density of the block and compare its weight with the upthrust.
Copy these into your notebook in your own words — that is how they stick.
Upward force from a fluid on a body.
Upthrust = weight of fluid displaced.
U = ρ_fluid V g.
Real weight − upthrust.
Average density < fluid density (W = U).
Average density > fluid density.
Hollow hull; low average density; displaces its weight of water.
Ballast tanks / hot or light gas.
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 solid block weighs 5.0 N in air. When fully submerged in water it appears to weigh 3.0 N. Take g = 10 N/kg and the density of water as 1 000 kg/m³.
(a) (a) State Archimedes’ principle. [2]
(b) (b) Calculate the upthrust on the block. [2]
(c) (c) Calculate the volume of the block. [3]
(d) (d) Calculate the mass and the density of the block. [4]
(e) (e) State, with a reason, whether the block floats or sinks in water. [2]
(f) (f) Explain why a steel ship floats. [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.