Mechanisms – Unit 3 | Student Worksheet

MULTIPLE CHOICE

Choose the best answer for each question.

Question 01

What is the primary function of a mechanism?

A To generate new energy from nothing B To transmit and transform force and motion C To store electrical energy for later use D To convert thermal energy into light

Mechanisms transmit and transform force and motion from an input source (motor) to an output receptor.

Question 02

The Law of the Lever states that a lever is in equilibrium when:

A F + d = R + r B F / d = R / r C F × d = R × r D F − d = R − r

The Law of the Lever: F × d = R × r, where F is the applied force, d is its distance from the fulcrum, R is the resistance, and r is its distance from the fulcrum.

Question 03

In a Class 2 lever, which element is between the fulcrum and the force?

A The resistance (load) B The fulcrum C The applied force D The torque point

In a Class 2 lever, the resistance is between the fulcrum and the applied force. A wheelbarrow is a classic example.

Question 04

A moveable pulley reduces the required force by what factor?

A F = R × 2 B F = R C F = R × 4 D F = R / 2

A moveable pulley gives a mechanical advantage of 2: you only need half the force (F = R/2), but you must pull the rope twice the distance.

Question 05

The transmission ratio formula for a gear system is N₂/N₁ = D₁/D₂. If the driving gear has 20 teeth (D₁) and spins at 60 rpm, and the driven gear has 40 teeth (D₂), what is N₂?

A 120 rpm B 30 rpm C 60 rpm D 15 rpm

N₂/N₁ = D₁/D₂ → N₂ = N₁ × D₁/D₂ = 60 × 20/40 = 30 rpm. The larger driven gear spins slower.

Question 06

What type of mechanism converts rotary motion into reciprocating linear motion (and vice versa)?

A Ratchet B Bearing C Crank and rod D Worm drive

A crank and rod mechanism transforms reciprocating motion into continuous rotary motion (like bicycle pedals) or vice versa (like car engine pistons).

Question 07

Which type of brake uses pads that press against a rotating disc attached to the wheel axle?

A Disc brake B Drum brake C Band brake D Ratchet brake

Disc brakes: a disc is connected to the axle, and brake pads press against the disc to create friction and slow the wheel.

Question 08

A worm drive (endless screw) is primarily used to:

A Increase rotational speed dramatically B Convert linear motion to rotary C Store energy like a spring D Reduce rotational speed

A worm drive is a special mechanism used to reduce rotational speed. It is found in guitar tuning pegs and lift mechanisms.

TRUE OR FALSE

Decide whether each statement is TRUE or FALSE. Click the button to select your answer.

01 A fixed pulley changes the direction of force but does not reduce the effort needed — the force applied equals the resistance.

02 Mechanisms can produce more energy than they receive if they are designed efficiently enough.

03 In a gear system, the relationship between speeds is inversely proportional to the number of teeth: the larger gear spins slower.

04 In a Class 1 lever, the resistance (load) is always between the fulcrum and the applied force.

05 A ratchet allows motion in only one direction, preventing movement in the opposite direction.

06 A rack and pinion mechanism converts rotary motion (pinion gear) into linear motion (rack), or vice versa.

07 When two meshing gears are in direct contact, they always rotate in the same direction.

08 A bicycle's free wheel mechanism allows the rear wheel to spin freely when the cyclist stops pedalling downhill.

FILL IN THE BLANKS

Complete each sentence using the words from the bank below.

📚 Word Bank

fulcrum torque transmission ratio input friction cam bearing clutch resistance crankshaft

01. The pivot point of a lever, around which the bar rotates, is called the .

02. The product of force multiplied by its distance from the fulcrum is known as .

03. The relationship between the speeds of two connected rotating wheels, expressed as N₂/N₁ = D₁/D₂, is called the .

04. All brake systems work by generating against a moving wheel to reduce its speed.

05. A is a rotating element on a shaft that pushes a follower bar up and down, converting rotary motion into reciprocating linear motion. It is found in sewing machines and combustion engines.

06. A is a support element that holds a rotating shaft in place while reducing friction, using metal balls or rollers.

07. A is a coupling device that can engage or disengage the power transfer from the engine to the transmission.

08. A synchronises the movements of multiple pistons in a car engine, converting their reciprocating motion into rotary motion.

LEVER PROBLEMS

Apply the Law of the Lever: F × d = R × r. Show your working in the space provided. Note: use g = 10 N/kg to convert kg to N.

LEVER 1 Class 1 Lever – Calculate Force

A 80 kg weight (R) is placed 25 cm from the fulcrum of a first-class lever. The effort is applied 120 cm from the fulcrum on the other side. What force (F) must be applied to lift the weight?

R = 80 kg × 10 = 800 N | r = 25 cm | d = 120 cm | F = ?

✏ Show your working:

Answer: F = N

LEVER 2 Class 1 Lever – Calculate Force

A 65 kg load is placed 45 cm from the fulcrum. If the force arm is 85 cm, what force is needed to balance the lever?

R = 65 kg × 10 = 650 N | r = 45 cm | d = 85 cm | F = ?

✏ Show your working:

Answer: F = N

LEVER 3 Class 2 Lever – Wheelbarrow

A wheelbarrow (Class 2 lever) carries a 45 kg load placed 25 cm from the wheel (fulcrum). The handles are 150 cm from the wheel. What force must be applied at the handles to lift the wheelbarrow?

R = 45 kg × 10 = 450 N | r = 25 cm | d = 150 cm | F = ?

✏ Show your working:

Answer: F = N

PULLEY PROBLEMS

Use the pulley formulas: Fixed: F = R | Moveable: F = R/2 | Compound: F = R/(2×n)

PULLEY 1 Moveable Pulley System

A system uses 2 moveable pulleys and 1 fixed pulley to lift a load of 6000 N. What force must be applied to the rope?

R = 6000 N | n = 2 moveable pulleys | Formula: F = R / (2 × n)

✏ Show your working:

Answer: F = N

PULLEY 2 Compound Pulley – Find Load

A person applies 250 N to the rope of a compound pulley system with 3 moveable pulleys. What is the maximum weight they can lift?

F = 250 N | n = 3 moveable pulleys | Formula: F = R / (2 × n) → R = F × 2 × n

✏ Show your working:

Answer: R = N

GEAR PROBLEMS

Use the transmission ratio: N₂/N₁ = Z₁/Z₂ (where Z = number of teeth). Determine speed and rotation direction.

GEAR 1 Transmission Ratio & Speed

Gear A (driving) has 15 teeth and spins at 10 rpm. Gear B (driven) has 15 teeth. Calculate the transmission ratio and the output speed of gear B.

Z₁ = 15 | Z₂ = 15 | N₁ = 10 rpm | N₂ = ?

✏ Show your working:

N₂ = rpm | System is: reducer / multiplier / neutral?

GEAR 2 Speed Calculation

A driving gear has 15 teeth and spins at 10 rpm. The driven gear has 45 teeth. What is the output speed? Is this system a reducer or multiplier?

Z₁ = 15 | Z₂ = 45 | N₁ = 10 rpm | N₂ = ?

✏ Show your working:

N₂ = rpm

GEAR 3 Three-Gear Train

A three-gear train: Gear A has 10 teeth at 60 rpm. Gear B has 20 teeth and meshes with A. Gear C has 40 teeth and meshes with B. What is the speed of gear C? What direction does C spin relative to A?

Z_A = 10, N_A = 60 rpm | Z_B = 20 | Z_C = 40 | N_C = ?

✏ Show your working (find N_B first, then N_C):

N_C = rpm | Direction relative to A: same / opposite?

Colegio Concertado Reina Sofía · Tecnología 3º ESO · Prof. Francisco Román Castro
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