CASE STUDY BASED QUESTION
Situation: During a school picnic at a lakeside, students observed the floating and sinking behaviour of different objects:
- (I) A small stone sank immediately.
- (II) A football floated but remained partially immersed.
- (III) A sealed water bottle barely floated, whereas the same bottle when empty and tightly capped floated easily.
- (IV) A heavy wooden log floated without difficulty.
Q1. Why does a heavier wooden log float while a small stone sinks?
Floating depends on density, not weight.
Wood has lower density than water, so it floats, while stone has higher density, so it sinks.
Wood has lower density than water, so it floats, while stone has higher density, so it sinks.
Q2. Why does a water-filled bottle barely float while an empty, capped bottle floats easily?
A water-filled bottle has greater mass and higher density, so it barely floats.
An empty bottle contains air, reducing its density, so it floats easily.
An empty bottle contains air, reducing its density, so it floats easily.
Q3. If you wrap the stone in a bubble wrap sheet, will it float or sink? Give a reason.
It may float because bubble wrap traps air, increasing volume and reducing average density below that of water.
Q4. If the students want to find the density of irregular stones found near the lakeside, which method should they use?
They should use the displacement method using a measuring cylinder to find volume.
Q5. Would the water-filled bottle float in a beaker of mercury? Give a reason.
Yes, it will float because mercury has very high density, so it provides greater buoyant force than water.
