Study Notes
Density is the mass per unit volume of a material. It determines whether an object will float or sink in a fluid based on its density relative to the fluid.
- Density — the mass per unit volume of a material. Example: A block of metal with a mass of 200g and a volume of 50cm³ has a density of 4g/cm³.
- Upthrust — an upward force exerted by a fluid on a submerged object. Example: A boat floats because the upthrust from the water is equal to the weight of the boat.
- Buoyancy — the ability of an object to float in a fluid. Example: Life jackets are designed to be buoyant, keeping a person afloat in water.
Exam Tips
Key Definitions to Remember
- Density: mass per unit volume
- Upthrust: upward force by a fluid on a submerged object
- Buoyancy: ability to float in a fluid
Common Confusions
- Confusing mass with density
- Thinking that heavier objects always sink
Typical Exam Questions
- How do you calculate the density of a liquid? Measure the mass and volume, then use the formula ρ = m/V.
- What determines if an object will float or sink? The object's density compared to the fluid's density.
- How can you find the volume of an irregularly shaped solid? Use water displacement in a measuring cylinder or eureka can.
What Examiners Usually Test
- Ability to calculate density using the formula ρ = m/V
- Understanding of how density affects buoyancy and floating
- Methods to determine the density of various materials