Learn by Novus · Open practice pack v1
Mechanical comprehension: applied practice: open practice pack: worked explanations
20 untimed questions across 4 authored sections.
This is untimed educational practice for one applied skill. It is not a clinical, diagnostic, employment, or professionally recognized assessment, it does not produce a score or credential, and for the judgement and safety families it is not a substitute for your employer's own policies, training, or legal duties.
Worked explanations
mechanical-comprehension-applied-s01-q01
Moments balance about the fulcrum: force x distance on one side equals force x distance on the other. 60 x 1 = F x 3, so F is the equivalent of 20 kg. The 180 kg answer multiplies where it should divide. That is the force you would need if the load were the one on the long arm.
mechanical-comprehension-applied-s01-q02
Directly meshed gears always turn in opposite directions, and speed varies inversely with tooth count: half the teeth means twice the speed, so 120 rpm counter-clockwise. Answers that keep the direction the same describe a belt or chain drive, not meshed teeth.
mechanical-comprehension-applied-s01-q03
Wheel (pivot), tray (load), handles (effort) sit in that order along the barrow, so the load is between the pivot and the effort: the second-class lever arrangement, which is why the handles need less force than the bricks weigh. 'Pivot between effort and load' describes a seesaw or a pair of scissors instead.
mechanical-comprehension-applied-s01-q04
Direction alternates at each mesh, so A clockwise makes B counter-clockwise and C clockwise again. Speed depends only on the first and last gear when the middle one is simply passed through: 20 teeth driving 10 teeth doubles the speed. The middle gear changes direction, not the overall ratio.
mechanical-comprehension-applied-s01-q05
An inclined plane's ideal mechanical advantage is its length divided by its height: 6 / 1.5 = 4. The 4.5 answer subtracts the height from the length, which is the horizontal run, not the ratio that matters.
mechanical-comprehension-applied-s02-q01
A fixed pulley does not move with the load, so no rope section other than the one holding the load takes any share of the weight: the only gain is that pulling down is easier to do with body weight than pulling up. Halving the force needs a movable pulley, where two rope sections support the load.
mechanical-comprehension-applied-s02-q02
Two supporting sections share the load, so the effort is halved to 100 N, but each section must shorten by 1 m, so 2 m of rope is pulled. The '100 N and 1 m' answer is the tempting one because it keeps the force saving and forgets the distance cost, which would mean getting energy for nothing.
mechanical-comprehension-applied-s02-q03
Mechanical advantage equals the number of rope sections supporting the moving block, so 600 N / 4 = 150 N. The 300 N answer counts only the two sections you can see moving fastest rather than all four that carry load.
mechanical-comprehension-applied-s02-q04
Mechanical advantage trades distance for force: halving the effort doubles the rope pulled, so work in still equals work out (a little more, once friction is counted). Answers that reduce the total work or the load's weight would create energy out of the rigging.
mechanical-comprehension-applied-s02-q05
Belt speed is common to both pulleys, so rpm varies inversely with diameter: 300 x (200 / 50) = 1200 rpm. An open belt keeps both pulleys turning the same way; only a crossed belt reverses the driven pulley.
mechanical-comprehension-applied-s03-q01
Pressure is the same throughout the fluid: 40 N / 2 cm squared = 20 N per cm squared, and 20 x 50 = 1000 N. The 500 N answer halves the area ratio, treating the input piston as 4 cm squared.
mechanical-comprehension-applied-s03-q02
Liquid pressure depends on depth and density only, so both bases sit at the same pressure despite very different volumes. Volume is the intuitive wrong answer: the wide tank holds far more water, but that extra weight is carried by the wider base, leaving pressure unchanged.
mechanical-comprehension-applied-s03-q03
The fluid is effectively incompressible, so the volume pushed out of the small cylinder equals the volume entering the large one: five times the area means one fifth of the travel, 4 cm. The 100 cm answer multiplies by the ratio, which would produce both more force and more distance.
mechanical-comprehension-applied-s03-q04
The same volume must pass every cross-section each second, so a smaller area forces a higher speed. 'Unchanged' confuses steady flow rate with steady velocity. The flow rate is constant, which is exactly why the velocity has to rise.
mechanical-comprehension-applied-s03-q05
A floating body displaces its own weight, so the submerged fraction equals the relative density: three quarters submerged means 0.75. The 0.25 answer reads off the part above the surface, which is the fraction that is not doing the supporting.
mechanical-comprehension-applied-s04-q01
The beam's own weight acts at its midpoint and splits evenly, giving 100 N per support. The crate is 1 m from the left and 3 m from the right, so the left support takes three quarters of it: 300 N. Total 400 N. The 300 N answer forgets the beam's own weight.
mechanical-comprehension-applied-s04-q02
Rolling friction is a small fraction of sliding friction for the same load, so rollers cut the required force sharply. Reducing the contact area is the plausible-sounding distractor, but dry friction depends on the normal force and the surface pair, not on how much area is touching, and a narrow end also makes the crate easy to tip.
mechanical-comprehension-applied-s04-q03
With the braking force held fixed by the question, a larger mass decelerates more slowly and carries more momentum, so it travels farther. The 'grip increases in proportion' answer is the real-world subtlety, but it only applies when braking is limited by tyre grip rather than by a stated fixed force.
mechanical-comprehension-applied-s04-q04
A single cylinder delivers power in short bursts; the flywheel's rotational inertia absorbs energy during the power stroke and releases it between strokes, so the shaft turns smoothly. It adds mass rather than reducing it, which is the point, a lighter flywheel smooths less.
mechanical-comprehension-applied-s04-q05
While that vertical line stays inside the base, gravity produces a restoring moment and the unit settles back; once it passes outside, the same weight becomes an overturning moment. Loading the top shelf heavily raises the centre of gravity and so reduces the tilt needed, but it is not by itself the tipping condition.