Physical Quantities & Measurement Techniques

Practice questions covering measurement techniques, scalars and vectors, and vector calculations based on Cambridge (CIE) IGCSE Physics.

To what precision can a ruler measure?

Rulers are able to measure to the nearest millimetre ($mm$).

What instrument is used to measure the volume of liquids?

Measuring cylinders.

How can a measuring cylinder be used to determine the volume of an irregular shape?

By measuring the change in volume of a liquid when the shape is added.

What is the typical human reaction time for an alert person?

Around $0.2$ to $0.3\,s$.

Why are multiple readings of measurements taken in physics?

To reduce the impact of measurement errors, improve precision, and reduce uncertainty.

How can the average thickness of a single sheet of paper be found precisely?

By measuring the thickness of 100 sheets of paper and dividing the result by 100.

What is the purpose of using a reference marker when measuring oscillations?

It provides a visual reference point, such as the equilibrium position, making it easier to see when the pendulum passes and reducing timing errors.

Define a scalar quantity.

A scalar quantity has only a magnitude.

Define a vector quantity.

A vector quantity has both magnitude and direction.

What is the difference between distance and displacement?

Distance is a scalar measure of the total length of the path taken, while displacement is a vector representing the distance between two points in a straight line in a stated direction.

What is the difference between speed and velocity?

Speed is a scalar measure of distance traveled per unit time, while velocity is a vector representing the speed of an object in a given direction.

Name four common vector quantities mentioned in the notes.

Displacement, velocity, force (including weight), acceleration, momentum, electric field strength, and gravitational field strength.

In a vector diagram, what do the length and direction of an arrow represent?

The length represents the magnitude and the direction of the arrow indicates the direction of the vector.

What theorem is used to find the magnitude of a resultant vector when two component vectors are at right angles?

Pythagoras' theorem ($F_R^2 = F_1^2 + F_2^2$).

What trigonometric function relates the opposite and adjacent sides to calculate the angle $\theta$ of a resultant vector?

$\tan(\theta) = \frac{\text{opposite}}{\text{adjacent}}$, therefore $\theta = \tan^{-1}\left(\frac{F_1}{F_2}\right)$.