Measuring Physical Quantities

Measuring Length

• Length can be measured using a ruler.

Measuring Time

• The period of one oscillation can be measured by timing 20 oscillations and dividing by 20.

Measuring Volume

• The volume of a cube or cuboid is found by measuring the length of its three sides and multiplying them together.
• The volume of a liquid can be measured using a measuring cylinder, where the bottom of the meniscus appears on the scale when viewed horizontally.

Displacement and Density

• All objects that sink in water displace their own volume of water.
• The volume of an irregularly shaped object can be found from the change in the height of liquid in a measuring cylinder when it is immersed.
• Density is the ratio of mass to volume for a substance: p = m/v.
• The density of water is 1000 kg/m3 or 1.0 g/cm3.

Buoyancy and Floating

• Anything less dense than water will float in water, and anything denser than water will sink.
• Ice floats because it is less dense than water.
• One liquid will float on top of another liquid if it is less dense.

Measuring Time Precisely

• Time can be measured using a clock or watch.
• Analogue clocks have hands and can only measure time to the nearest second.
• Digital clocks display numbers and record time to a precision of at least one hundredth of a second.