Loading chapter

Academiq Edu

Learn

Home

Subjects

Simulations

Miqo Tutor

Practise

Mock exams

Past papers

Revision vault

Track

My progress

Study planner

Academiq Edu

Physical quantities and units

1/3

Physical quantities and units

3 interactive labs · AS & A Level Physics 9702

Base Units Builder

1.2 SI units · Build derived units from kg, m, s and A with power sliders, then check whether physics equations are homogeneous.

Loading simulation…

About this lab

Build derived units from kg, m, s and A with power sliders, then check whether physics equations are homogeneous.

You will be able to

Express derived units as products or quotients of the SI base units.
Use base units to check the homogeneity of a physical equation.
Explain why a homogeneous equation is not necessarily correct.

Examiner's note. Work from a defining equation, one step at a time: N = kg m s⁻² from F = ma, then J = N m = kg m² s⁻². Only kg, m, s, A, K and mol are base units: the volt and the newton are derived. Homogeneous means both sides reduce to the same base units; it cannot show a pure number such as ½ or 2π is wrong.

Uncertainty Lab

1.3 Errors and uncertainties · Measure a metal cylinder with a balance, micrometer or ruler, and combine the uncertainties to find its density.

Loading simulation…

About this lab

Measure a metal cylinder with a balance, micrometer or ruler, and combine the uncertainties to find its density.

You will be able to

Determine the percentage uncertainty in a measurement from the instrument resolution or the spread of repeat readings.
Calculate the uncertainty in a derived quantity by adding percentage uncertainties, doubling for a square.
Distinguish between random and systematic errors, and between precision and accuracy.

Examiner's note. For ρ = 4m/(πd²l), %ρ = %m + 2 × %d + %l: the square doubles the diameter term, and the constants 4 and π carry no uncertainty. Give the absolute uncertainty to 1 significant figure and the value to the same decimal place. Repeating readings reduces random error only: a zero error is systematic and must be found and subtracted.

Vector Components Lab

1.4 Scalars and vectors · Resolve two coplanar vectors into components, add them and find the resultant's magnitude and direction.

Loading simulation…

About this lab

Resolve two coplanar vectors into components, add them and find the resultant's magnitude and direction.

You will be able to

Resolve a vector into two perpendicular components, F cos θ and F sin θ.
Determine the resultant of two coplanar vectors by adding components or by a scale drawing.
Deduce the condition for two forces to have a zero resultant.

Examiner's note. Measure each angle from one stated reference direction, then F_x = F cos θ and F_y = F sin θ with signs. Add the x components and the y components separately, then R = √(ΣF_x² + ΣF_y²) and tan θ = ΣF_y/ΣF_x. The classic slip is adding the magnitudes: 10 N and 10 N at 120° give only 10 N.

Revise the theoryFull revision notes for Physical quantities and units.Test yourselfExam-style questions for this chapter.