Unit D: Mechanical Systems

Key Ideas     Unit Checklist

Pre-assessment: What do you know?


Figure D.P.1 – A construction crane contains simple machines like pulleys, to lift heavy loads.

Figure D.P.2 – Simple machines reduce the amount of force required to lift objects.


Figure D.P.3 – Engineers build new machines to improve our lives.
Humans use machines every day to help us do work with less effort. Some machines are very simple. Other machines are complex and have many parts. We can calculate the exact advantage of using a machine compared to doing the work by hand.

People change and improve machines over time. We no longer use some machines that people used in the past. Engineers and scientists are constantly inventing new machines that will improve our lives in the future.

What machines do you use everyday? How do these machines make tasks easier? What useful machines do you think will be invented in the future?


Figure D.P.4 – We rely on machines for fast transportation.

Figure D.P.5 – The design of machines changes over time.

Pre-assessment Questions & Hints

Step 1: The Questions


This short pre-assessment is to find out what you might already know about the topic of mechanical systems. Below are four questions. Think about them! If you need a hint, click on the question.

Optional: If you would like a place to write your answers, download this document.
Think about the parts that many machines have in common.
Think about the effort required to move a box up a ramp compared to lifting it straight up.
Think about the hoses attached to the digging arm of the excavator.
Think about news reports that you might have seen about new machines.

Step 2: The Answers

 Click each of the suggested answers below – how do they compare to your thoughts and answers?
Six simple machines are:
  • Lever
  • Inclined plane
  • Screw
  • Pulley
  • Wedge
  • Wheel and axle
Pushing a heavy box up a ramp requires the same amount of energy, or work, as lifting the box straight up. However, pushing a heavy box up a ramp reduces the amount of force required to move the box.
An excavator digging arm uses a hydraulic system to move. Hydraulic hoses on the digging arm contain fluid. The machine operator uses levers to apply force to the hydraulic fluid in the hoses. The hydraulic fluid transfers force to the excavator arm, causing it to move.
One example of a new machine is the drone. A drone is a small robotic aircraft that doesn’t need a pilot. Another example of a new machine is the driverless car, which is a vehicle controlled by a computer.

Step 3: Check In With Your Teacher

The start of a new unit is a great time to touch base with your teacher! Here are just a few reasons to consider contacting your teacher:

  1. Perhaps you found this pre-assessment quiz very easy because you have studied this material before, such as at another school. If so, it's important to tell your teacher.

  2. It's very good for your teacher to know you are starting a new unit; it will give them a good idea of your progress. It doesn't have to be a long message, just a "I'm starting Unit D; just thought you might want to know!"

  3. Your teacher may have special tips and suggestions for the unit you are starting.

  4. Just to say hi – your teacher always enjoys hearing from you!

To contact your teacher, post in the Course Questions Forum, send your teacher an email, or call on the phone if you like. Whatever way you choose, it's always a good idea to get in touch with your teacher – make sure you do it frequently.