| Exam Board | OCR MEI |
|---|---|
| Module | Further Mechanics A AS (Further Mechanics A AS) |
| Year | 2021 |
| Session | November |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Dimensional Analysis |
| Type | Find dimensions of compound quantity |
| Difficulty | Easy -1.2 Part (a) is a straightforward dimensional analysis requiring only the substitution of J = ML²T⁻² and kg = M to get L²T⁻². Part (b) is simple unit conversion arithmetic with given conversion factors. Both parts require only direct application of definitions with no problem-solving or conceptual insight. |
| Spec | 6.01b Units vs dimensions: relationship |
| Answer | Marks | Guidance |
|---|---|---|
| 1 | (a) | [ Energy ]=M ( LT −1 )2 or M⋅LT −2⋅L or ML2T −2 |
| Answer | Marks | Guidance |
|---|---|---|
| Specific energy | A1 | 1.1 |
| Answer | Marks | Guidance |
|---|---|---|
| (b) | 345÷4÷28.35×40×4184 | M1 |
| Answer | Marks | Guidance |
|---|---|---|
| ≈509,000J | A1 | 2.2b |
Question 1:
1 | (a) | [ Energy ]=M ( LT −1 )2 or M⋅LT −2⋅L or ML2T −2 | M1 | 1.2 | Any form acceptable. This mark
may be implied by the correct
answer.
[ ]=ML2T −2⋅M −1=L2T −2
Specific energy | A1 | 1.1
[2]
(b) | 345÷4÷28.35×40×4184 | M1 | 1.1 | All scale factors present. Allow one
×/÷
slip with .
≈509,000J | A1 | 2.2b
[2]1 The specific energy of a substance has SI unit $\mathrm { J } \mathrm { kg } ^ { - 1 }$ (joule per kilogram).
\begin{enumerate}[label=(\alph*)]
\item Determine the dimensions of specific energy.
A particular brand of protein powder contains approximately 345 Calories (Cal) per 4 ounce (oz) serving. An athlete is recommended to take 40 grams of the powder each day.
You are given that $1 \mathrm { oz } = 28.35$ grams and $1 \mathrm { Cal } = 4184 \mathrm {~J}$.
\item Determine, in joules, the amount of energy in the athlete's recommended daily serving of the protein powder.
\end{enumerate}
\hfill \mbox{\textit{OCR MEI Further Mechanics A AS 2021 Q1 [4]}}