Royal Navy Recruiting Test (RT) Mechanical Comprehension Test Syllabus

Mechanical Comprehension Test syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Mechanical Comprehension Test in Royal Navy Recruiting Test (RT), not a summary of it.

1. 1

   Forces and Motion

   4 topics

   • Balanced and unbalanced forces
     • Identifying resultant force direction
     • Equilibrium of objects
   • Weight, mass and gravity
   • Friction and its effects
     • Surfaces and resistance
     • Reducing friction
   • Speed, acceleration and momentum basics
2. 2

   Simple Machines and Mechanical Advantage

   5 topics

   • Levers and the principle of moments
     • First, second and third class levers
     • Fulcrum, load and effort
     • Balancing seesaw problems
   • Pulleys and pulley systems
     • Single fixed and movable pulleys
     • Block and tackle effort calculations
   • Gears and gear trains
     • Gear ratios and turning direction
     • Speed versus torque trade-off
   • Inclined planes, wedges and screws
   • Wheels, axles and winches
3. 3

   Pressure, Fluids and Hydraulics

   4 topics

   • Pressure as force over area
   • Hydraulic systems and force multiplication
     • Master and slave piston relationships
     • Brake and jack principles
   • Floating, sinking and buoyancy
   • Pneumatics and compressed air basics
4. 4

   Energy, Work and Power

   4 topics

   • Kinetic and potential energy
   • Conservation and transfer of energy
   • Work done and mechanical power
   • Springs, tension and compression
5. 5

   Structures, Materials and Tools

   4 topics

   • Centre of gravity and stability
     • Toppling and base width
     • Loading of beams and supports
   • Properties of common materials
   • Hand tools and their correct use
   • Cogs, belts and chain drives
6. 6

   Everyday and Naval Mechanical Scenarios

   4 topics

   • Interpreting mechanical diagrams
   • Predicting movement in linked systems
     • Belt-and-pulley rotation direction
     • Linkage and crank motion
   • Valves, taps and flow control
   • Practical lifting and rigging problems

Mechanical Comprehension Test flashcards for Royal Navy Recruiting Test (RT)

20 of 51 cards from the Mechanical Comprehension Test deck — real questions with worked answers.

1. What is the difference between balanced and unbalanced forces, and what does each produce?

   Balanced forces are equal in size and opposite in direction, giving a net (resultant) force of zero, so an object stays still or moves at constant velocity. Unbalanced forces give a non-zero resultant, causing acceleration (a change in speed or direction).

2. State Newton's second law as a formula relating force, mass and acceleration.

   $F = ma$, where force $F$ is in newtons (N), mass $m$ in kilograms (kg) and acceleration $a$ in $\mathrm{m/s^{2}}$.

3. What is the difference between mass and weight?

   Mass is the amount of matter in an object (in kg) and is the same everywhere. Weight is the gravitational force on that mass (in N) and changes with the strength of gravity.

4. How is weight calculated from mass, and what is the value of gravity used on Earth?

   $W = mg$, where $g \approx 9.81\ \mathrm{m/s^{2}}$ on Earth (often rounded to $10\ \mathrm{m/s^{2}}$). A $10\ \mathrm{kg}$ mass weighs about $98\ \mathrm{N}$.

5. What is friction and in which direction does it act?

   Friction is a resistive force between two surfaces in contact. It always acts opposite to the direction of motion (or attempted motion), opposing sliding.

6. Name two useful effects and two unwanted effects of friction.

   Useful: grip for walking/braking, and allowing gears/belts to drive. Unwanted: wear of parts, and heat/energy loss reducing efficiency.

7. How can friction be reduced in machinery?

   By lubrication (oil/grease), using smoother surfaces, fitting bearings or rollers, and reducing the contact load.

8. Define speed and give its formula.

   Speed is distance travelled per unit time: $v = \dfrac{d}{t}$, measured in $\mathrm{m/s}$.

9. Define acceleration and give its formula.

   Acceleration is the rate of change of velocity: $a = \dfrac{\Delta v}{t}$, measured in $\mathrm{m/s^{2}}$.

10. What is momentum and how is it calculated?

    Momentum is the quantity of motion of a moving object: $p = mv$ (mass times velocity), measured in $\mathrm{kg\,m/s}$.

11. What is a lever, and what are its three parts?

    A lever is a rigid bar that turns about a fixed point. Its three parts are the fulcrum (pivot), the effort (force applied) and the load (resistance to be moved).

12. State the principle of moments for a balanced (equilibrium) lever.

    For balance, total clockwise moments equal total anticlockwise moments about the pivot: $F_{1} d_{1} = F_{2} d_{2}$.

13. How is the moment of a force calculated?

    Moment $=$ force $\times$ perpendicular distance from the pivot: $M = F \times d$, measured in newton-metres (N·m).

14. Classify the three orders (classes) of levers by the arrangement of fulcrum, load and effort.

    1st class: fulcrum between effort and load (seesaw). 2nd class: load between fulcrum and effort (wheelbarrow). 3rd class: effort between fulcrum and load (tweezers/forearm).

15. On a balanced seesaw, a $40\ \mathrm{N}$ child sits $2\ \mathrm{m}$ from the pivot. How far must a $20\ \mathrm{N}$ child sit on the other side?

    Using $F_{1}d_{1}=F_{2}d_{2}$: $40 \times 2 = 20 \times d$, so $d = \dfrac{80}{20} = 4\ \mathrm{m}$.

16. How does a single fixed pulley help, and does it give a mechanical advantage?

    A single fixed pulley changes the direction of the force (you pull down to lift up) but gives no mechanical advantage; the effort equals the load.

17. How does the mechanical advantage of a pulley system relate to the number of supporting rope sections?

    Mechanical advantage equals the number of rope sections directly supporting the load. With $n$ supporting ropes, effort $= \dfrac{\text{load}}{n}$ (ignoring friction).

18. In a pulley system with 4 supporting rope sections, what effort is needed to lift a $200\ \mathrm{N}$ load (ignoring friction)?

    Effort $= \dfrac{200}{4} = 50\ \mathrm{N}$, but the rope must be pulled $4\times$ the distance the load rises.

19. For two meshing gears, how do their sizes affect speed and turning direction?

    Two meshing gears turn in opposite directions. A smaller driven gear turns faster; a larger driven gear turns slower. Speed is inversely proportional to the number of teeth.

20. How is the gear ratio of a gear train calculated?

    Gear ratio $= \dfrac{\text{teeth on driven gear}}{\text{teeth on driver gear}}$. A driver of 10 teeth turning a driven of 30 teeth gives a ratio of $3:1$ (driven turns once per 3 driver turns).

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