A-Level · Mathematics · AQA · Mark scheme decoded
AQA A-Level Mathematics: Quantities and Units in Mechanics — mark scheme explained
The short answer
In mechanics, understanding the fundamental quantities and units is crucial for solving problems accurately. The International System of Units (SI) provides a standardized framework for these measurements. This section covers both fundamental and derived quantities and their respective units. Fundamental Quantities and Units Length: Measured in meters (m).
The question
A car travels a distance of 150 meters in 10 seconds. Calculate its velocity. [Paraphrased for study — not reproduced from any exam paper.]
Mark scheme, decoded
What each mark is really for — in plain English — and the wording trap that loses it.
- S1
Identify the given values: Distance (d) = 150 m, Time (t) = 10 s
- S2
Use the formula for velocity: v = d / t
- S3
Substitute the values: v = 150 m / 10 s
- S4
Calculate the result: v = 15 m/s
Model answer
Worked through, with each step tagged to the mark it earns.
- S1
Identify the given values: Distance (d) = 150 m, Time (t) = 10 s
- S2
Use the formula for velocity: v = d / t
- S3
Substitute the values: v = 150 m / 10 s
- S4
Calculate the result: v = 15 m/s
Final answer: 15 m/s
Common mistakes
- Confusing velocity with speed. — Always specify the direction when dealing with velocity.
- Using incorrect units for acceleration. — Ensure you use the correct unit for acceleration: m/s 2 .
- Forgetting to convert units before calculations. — Always check and convert all measurements to consistent units before performing calculations.
- Using mass instead of weight in force calculations. — Use the formula W = m × g to convert mass to weight when necessary.
- Incorrectly calculating moment by using the wrong distance. — Ensure you use the correct perpendicular distance when calculating moment.
- Forgetting that acceleration due to gravity is negative for downward motion. — Always consider the direction of acceleration when solving problems involving gravity.
Where the marks go
- Full worked solution (all marking points)3 marks