A driving gear has 20 teeth and meshes with a driven gear that has 60 teeth. What is the gear ratio?

1:3 — the driven shaft rotates three times for every revolution of the driving shaft 3:1 — the driven shaft rotates once for every three revolutions of the driving shaft 1:1 — gear ratio only changes when the number of teeth on both gears is identical 6:1 — gear ratio equals the sum of both gears' teeth divided by the smaller gear

When you select a low gear on a bicycle, you use a small chainring (few teeth) and a large sprocket (many teeth). What is the effect?

Wheel rotates faster than the pedals, ideal for steep uphill climbs Pedalling speed produces slower wheel rotation but with more torque — easier to climb hills The chain is bypassed to give maximum mechanical advantage Friction between tyres and road increases to prevent slipping

Spur gears are the simplest and most common gear type. They are characterised by:

Curved teeth on conical surfaces, connecting shafts at right angles Straight teeth cut parallel to the gear axis, connecting shafts on parallel axes A helical thread on a cylindrical worm shaft engaging a flat wheel Rack-and-pinion teeth for converting rotation to linear motion only

Bevel gears are used in a car's rear axle differential because they:

Connect shafts at an angle (usually 90°) to change the direction of rotation Provide very high gear ratios in a single small package Are self-locking so the car cannot roll backwards Connect parallel shafts and are quieter than spur gears at high speed

A worm gear drive consists of a helical screw (worm) meshing with a toothed wheel (worm wheel). Which statement best describes its unique property?

It doubles speed in a single stage and is used in high-performance racing transmissions It provides very large speed reductions and is self-locking — the worm wheel cannot drive the worm It connects two parallel shafts that are separated by a large distance It eliminates the need for lubrication at high temperatures

Why is a chain drive preferred over a belt drive for a bicycle transmission?

Chains are lighter than belts, reducing overall bicycle weight Chains absorb vibration better than rigid belt drives A chain cannot slip on its sprocket teeth, ensuring positive (no-slip) power transmission Chains are cheaper and easier to replace than toothed belts

An engineer needs to transmit power between two parallel shafts that are 500 mm apart — too far for direct gearing. Which drive system is most appropriate?

A single very large spur gear spanning the full distance A magnetic coupling that transmits force without contact Belt or chain drive, which can bridge large distances between shafts A fluid coupling using hydraulic pressure through a pipe

If a motor delivers 200 Nm of torque and drives a gear train with a 4:1 speed reduction ratio, what torque is available at the output shaft (assuming 100% efficiency)?

50 Nm 200 Nm 400 Nm 800 Nm

Belt drives are commonly used in washing machine drum drives rather than gear drives because belts:

Can transmit more torque than any gear system of the same size Never stretch or degrade over the life of the appliance Absorb vibration and shock, operate quietly, and allow some slip that protects the motor if the load jams Are self-tensioning and require no maintenance

A gear system can increase torque or increase speed, but not both at the same time. This is a consequence of:

Newton's third law — every action has an equal and opposite reaction Conservation of energy — power (torque × speed) cannot be increased by a passive mechanical system The material strength of steel teeth limiting maximum load Lubrication requirements that cap maximum rotational speed

Helical gears are used in car gearboxes in preference to spur gears because helical gears:

Provide higher gear ratios in a single mesh than spur gears Are self-locking and prevent the car rolling backwards Engage gradually along the tooth face, running more quietly and smoothly under load Do not require lubrication because helical teeth generate less heat

In a clock mechanism, a large wheel drives a small pinion. The pinion turns faster than the wheel. This is an example of:

Speed reduction — the gear ratio is greater than 1, multiplying torque Self-locking — the pinion prevents the wheel from reversing Speed increase — the gear ratio is less than 1, trading torque for higher rotational speed Neutral — there is no change in speed when gears of different sizes mesh