Mechanism Questions

Mastering the technology component is where you transform your design from a static shape into a functional, working solution. In the O Level syllabus, this is about understanding how to control energy, motion, and forces to make a product "do" something. ⚙️

We focus on three main pillars of technology:

1. Mechanisms ⚙️

This is the study of moving parts. You learn how to convert one type of motion (like the spinning of a motor) into another (like the back-and-forth movement of a gripper). Key concepts include Levers, Linkages, Gears, and Cams. For example, a simple pair of scissors is actually a first-class lever!

Mechanism Questions 

Theme: School Library Book Sorting Machine

A new automated system is being designed for the school library to sort returned books by shelf category. A key part of this system is a mechanism that can transport books from a drop-off point to a sorting conveyor.

Question 1 (a) State one function of a follower in a cam mechanism. [1]

(b) Explain how a worm and wheel gear system can be used to prevent a book transport belt from moving backward. [2]

(c) A simple pulley system is used to lift books onto the sorting conveyor. State two ways to increase the mechanical advantage of this pulley system. [2]

Question 2 (a) A gear train is used to reduce the speed of the motor driving the conveyor belt. The driver gear has 40 teeth and rotates at 120 rpm. The driven gear has 120 teeth. Calculate the speed of the driven gear. Show your workings. [4]

(b) The transport mechanism uses a four-bar linkage to push books onto the conveyor. Draw a sketch of a four-bar linkage and label its key components: fixed link, crank, connecting rod, and rocker. [4]

Question 3 (a) Describe the function of a clutch in a mechanical system, using an example from the book sorting machine scenario. [2]

(b) A ratchet and pawl mechanism is used in the book transport system. Describe a practical application of this mechanism within the book sorting machine. [2]

(c) State one disadvantage of using a friction-based system like a belt drive over a gear system. [1]

--- End of Section B ---

Mechanism Questions

Answer Key: 

Total marks: 18

Theme: School Library Book Sorting Machine

Question 1 (a) State one function of a follower in a cam mechanism. [1]

• Possible Answer: To convert the rotary motion of the cam into linear or oscillating motion.

(b) Explain how a worm and wheel gear system can be used to prevent a book transport belt from moving backward. [2]

• Possible Answer: The worm and wheel gear system has a self-locking property. The worm can easily turn the wheel, but the wheel cannot turn the worm due to the steep angle of the worm's teeth and friction. Therefore, once the motor stops, the worm prevents the wheel and the attached transport belt from reversing.

(c) A simple pulley system is used to lift books onto the sorting conveyor. State two ways to increase the mechanical advantage of this pulley system. [2]

• Possible Answer:

  1. Increase the number of pulleys in the system.

  2. Increase the number of ropes or belts supporting the load.

Question 2 (a) A gear train is used to reduce the speed of the motor driving the conveyor belt. The driver gear has 40 teeth and rotates at 120 rpm. The driven gear has 120 teeth. Calculate the speed of the driven gear. Show your workings. [4]

• Possible Answer:

  • Formula: Gear Ratio (GR) = Number of teeth on driven gear / Number of teeth on driver gear

  • GR = 120 / 40 = 3

  • Formula: Speed of driven gear = Speed of driver gear / Gear Ratio

  • Speed = 120 rpm / 3 = 40 rpm

  • The speed of the driven gear is 40 rpm.

(b) The transport mechanism uses a four-bar linkage to push books onto the conveyor. Draw a sketch of a four-bar linkage and label its key components: fixed link, crank, connecting rod, and rocker. [4]

• Possible Answer:

  • The sketch should show four rigid links connected by four revolute joints, forming a closed loop.

  • The fixed link (ground) should be clearly indicated.

  • The crank (the input link that rotates 360 degrees) should be labelled.

  • The rocker (the output link that oscillates back and forth) should be labelled.

  • The connecting rod (the link joining the crank and rocker) should be labelled.

Question 3 (a) Describe the function of a clutch in a mechanical system, using an example from the book sorting machine scenario. [2]

• Possible Answer: A clutch is a mechanism that connects or disconnects a rotating drive shaft to a driven shaft. In the book sorting machine, a clutch could be used to temporarily disengage the motor from the conveyor belt when a book needs to be held in place for sorting, without the need to switch the motor off and on.

(b) A ratchet and pawl mechanism is used in the book transport system. Describe a practical application of this mechanism within the book sorting machine. [2]

• Possible Answer: A ratchet and pawl mechanism could be used to ensure that a book transport arm only moves in a single direction (e.g., forward) and cannot slip backward under the weight of a book or during a power outage.

(c) State one disadvantage of using a friction-based system like a belt drive over a gear system. [1]

• Possible Answer: Belt drives can slip, which can lead to a loss of power transmission and inaccurate timing, whereas gears provide a positive drive without slippage.