Physical Quantities and Measurement TechniquesCambridge IGCSE Physics: Flashcards

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What is a scalar quantity? Give two examples.

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What is a scalar quantity? Give two examples.: A scalar quantity has magnitude only (no direction). Examples include: distance, speed, time, mass, energy and temperature.
What is a vector quantity? Give two examples.: A vector quantity has both magnitude and direction. Examples include: force, weight, velocity, acceleration, momentum, electric field strength and gravitational field strength.
Describe how to use a ruler to measure a length.: Place the ruler along the object to be measured, ensuring it is aligned straight. Read the measurement at both ends of the object and calculate the difference. Record to the appropriate number of significant figures based on the ruler's scale divisions.
Describe how to use a measuring cylinder to find a volume.: Pour the liquid into the measuring cylinder and read the volume at the meniscus (curved surface). Read the scale at eye level. The reading is taken at the bottom of the meniscus for most liquids.
Name three different ways to measure time intervals in a laboratory.: Clocks, digital timers, and stopwatches can be used to measure time intervals. Digital timers are most accurate for short intervals.
Why is it better to measure multiple oscillations rather than a single oscillation of a pendulum?: Measuring multiple oscillations reduces the percentage uncertainty in the measurement. Timing errors (such as reaction time) have less effect on the final result when divided by the number of oscillations.
Explain the method to determine the period of a pendulum by measuring multiple oscillations.: Time at least 20 complete oscillations using a digital timer or stopwatch. Divide the total time by the number of oscillations to find the period. Repeat several times and calculate an average value to reduce uncertainty.
What is meant by finding an 'average value' for a measurement?: Taking multiple measurements of the same quantity and calculating the mean (total ÷ number of measurements). This reduces random errors and uncertainty in the final result.
How would you measure a small distance such as the diameter of a wire using a ruler?: Measure the width of multiple (e.g. 10) loops of wire laid side by side. Divide the total width by the number of loops to find the diameter of one wire, reducing measurement uncertainty.
State which of the following are scalar quantities: velocity, mass, force, speed.: Scalar quantities: mass and speed. Vector quantities: velocity and force.
Describe how to find the resultant of two forces at right angles to each other by calculation.: Use Pythagoras' theorem: R² = F₁² + F₂², where R is the resultant force and F₁ and F₂ are the two forces at right angles. Calculate R = √(F₁² + F₂²).
Describe how to find the resultant of two velocities at right angles graphically.: Draw the first velocity as a straight line to scale. From the end of this line, draw the second velocity at right angles to scale. Draw a line from the start to the end point. This line represents the resultant velocity in magnitude and direction.
What is the difference between distance and displacement?: Distance is a scalar quantity (magnitude only) representing the total path travelled. Displacement is a vector quantity (magnitude and direction) representing the straight-line distance from start to finish point.
Why is weight a vector quantity but mass a scalar quantity?: Mass (scalar) is the amount of matter in an object. Weight (vector) is the gravitational force acting on the mass and always acts downwards, so it has both magnitude and direction.
Name two scalar quantities and two vector quantities from the specification.: Scalar quantities: distance, speed (or time, mass, energy, temperature). Vector quantities: force, velocity (or weight, acceleration, momentum, electric field strength, gravitational field strength).