krit.club logo

Motion, Forces and Energy - Physical quantities and measurement techniques

Grade 11A LevelPhysics

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Base quantities in physics include length (mm), mass (kgkg), time (ss), temperature (KK), and electric current (AA).

•

Derived quantities are calculated from base quantities, such as density (ρ\rho), speed (vv), and volume (VV).

•

A micrometer screw gauge is used for measuring very small distances, typically providing precision to 0.01 mm0.01 \text{ mm}.

•

A vernier calliper provides measurements precise to 0.1 mm0.1 \text{ mm} for internal and external diameters.

•

Scalar quantities have only magnitude (e.g., distance, speed, time, mass), while Vector quantities have both magnitude and direction (e.g., displacement, velocity, acceleration, force).

•

Density is defined as the mass per unit volume of a substance: ρ=mV\rho = \frac{m}{V}.

•

The volume of an irregular solid can be determined using the displacement method with a measuring cylinder and a liquid.

•

To improve accuracy in timing experiments (like a pendulum), measure the time for multiple oscillations (nn) and divide by nn to find the period (TT).

📐Formulae

ρ=mV\rho = \frac{m}{V}

Vrectangular prism=l×w×hV_{rectangular\ prism} = l \times w \times h

Vcylinder=πr2hV_{cylinder} = \pi r^2 h

T=ttotalnT = \frac{t_{total}}{n}

💡Examples

Problem 1:

An object has a mass of 480 g480 \text{ g} and a volume of 60 cm360 \text{ cm}^3. Calculate its density in kg/m3kg/m^3.

Solution:

First, convert mass to kgkg: m=480 g=0.48 kgm = 480 \text{ g} = 0.48 \text{ kg}. Next, convert volume to m3m^3: V=60 cm3=60×(10−2 m)3=60×10−6 m3=6×10−5 m3V = 60 \text{ cm}^3 = 60 \times (10^{-2} \text{ m})^3 = 60 \times 10^{-6} \text{ m}^3 = 6 \times 10^{-5} \text{ m}^3. Calculate density: ρ=0.48 kg6×10−5 m3=8000 kg/m3\rho = \frac{0.48 \text{ kg}}{6 \times 10^{-5} \text{ m}^3} = 8000 \text{ kg/m}^3.

Explanation:

To convert density from g/cm3g/cm^3 to kg/m3kg/m^3, you multiply by 10001000. Alternatively, convert units individually before using the formula ρ=mV\rho = \frac{m}{V}.

Problem 2:

A student uses a stopwatch to time 2020 swings of a pendulum. The total time recorded is 35.4 s35.4 \text{ s}. Determine the period TT of the pendulum.

Solution:

Using the formula T=ttotalnT = \frac{t_{total}}{n}: T=35.4 s20=1.77 sT = \frac{35.4 \text{ s}}{20} = 1.77 \text{ s}.

Explanation:

Measuring multiple oscillations reduces the effect of human reaction time errors, leading to a more accurate value for a single period TT.