Unit D Review

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  Review

On the next page, you will take a 35-question unit test. Are you confident you know the Unit D material well?


It's always a good idea to make sure you are prepared for a test by studying. You can do this by returning to the Table of Contents and reviewing any Unit D lessons you are not sure about.


Also, you can review unit D material by trying three review exercises.

  1. Create a mind map of the unit material. A mind map is a visual representation of how all the ideas and concepts of the unit connect with each other. Try building a mind map by clicking the first tab below.

  2. Do a puzzle! A puzzle can be a fun way to review unit concepts or terms. Try the puzzle we have prepared for you by clicking the second tab below.

  3. Practice answering some questions. We have prepared some questions that will really get you thinking about the unit material. Try the practice questions by clicking the third tab below.


Remember, these are just suggestions for review! In addition to doing these three review exercises, you might also:

  • Contact your teacher for assistance if you are not sure about any concepts.
  • Check the course glossary and read all the unit D terms.
  • Make your own study cards and test yourself.


Whatever you choose to do, good luck with your unit review!

Make a Mind Map
A mind map is a visual representation of how all the ideas and concepts of the unit connect with each other. There are several ways you can create a mind map:

  • You can create a mind map simply with just a pen and a sheet of paper.
  • You might try to build one using a free drawing program such as GIMP.
  • You can use a web-based free mind map generator such as MindMup. MindMup is pretty easy to figure out just by playing with it, but click here if you want to view a short tutorial.
As an example to get you started, below you will see the start of a mind map for Unit D that was built using MindMup. You can re-create it and build on it, or create a completely new one of your own.




Do a Puzzle
A puzzle can be a fun way to review unit concepts or terms. We have prepared a Unit D review puzzle for you, and there are several ways you can make the most of it:


 


Complete Review Questions
The following 5 questions are meant to get you thinking about the Unit D material. Answers are provided below each question, but before you look at the answer, you should really try hard at answering the question yourself. If you have to, review the Unit D lessons.


Question 1
2 marks

Describe an everyday task that would be much more difficult without a machine.
Explain how the machine makes the task easier.

2 marks total
1 mark per description, 1 mark per explanation

Sample answer:
  • Travelling from one place to another would be very difficult without automobiles, like cars. Not having automobiles would require walking or bicycling from one place to another. Using a car requires much less physical effort and time than walking or bicycling.


Question 2
6 marks

A man needs to lift a heavy box up onto a theatre stage, which is 2 metres high. To lift the box straight up onto the stage, it takes 600 N of force.

The man has two machines available to make the job easier:
  1. He can push the box up a 5-metre long ramp using 400 N of pushing force.
  2. He can hook the box to a pulley system and pull a rope 5 m, using 300 N of pulling force.

  • Calculate the output work needed to lift the box directly.
  • Calculate the input work done by each machine.
  • Which machine would be more efficient to use? Show calculations to prove your answer.

6 marks total
1 mark for calculated input work
2 marks per calculated output work
2 marks per calculated efficiency
1 mark for stated machine with greater efficiency

Output work to lift box = force x distance = 600 N x 2 m = 1200 J

Input work to lift box using ramp = force x distance = 400 N x 5 m = 2000 J

Input work to lift box using pulleys = force x distance = 300 N x 5 m = 1500 J

Efficiency using ramp = output work/ input work = 1200 J / 2000 J x 100 = 60%

Efficiency using pulleys = output work/ input work = 1200 J / 1500 J x 100 = 80%

The pulley system has a greater calculated efficiency, so it would be more efficient to use.


Question 3
2 marks

Car brakes are a hydraulic system. Pushing down with a small force on a car’s brake pedal applies pressure to the brake fluid. The brake fluid transfers pressure to brake pads, which press against the car’s wheels. The brake pads transfer a large friction force to stop the car.

 

Explain why a driver must push down a larger distance on the brake pedal compared to the smaller distance that the brake pads move.
 
2 marks total
1 mark for identification of pistons, 1 mark for connection of small force to large distance

  • In this hydraulic system, the brake pedal is the input piston and the brake pads are the output piston.
  • A hydraulic brake system multiplies the small force on a brake pedal into a large force on the brake pads, to stop the car. However, the trade-off of applying a small force to the input piston is that the input piston (brake pedal) must be moved a larger distance compared to the output piston (brake pads).



Question 4
2 marks

A clothes iron is a machine that removes wrinkles from clothes. A scientist invents a new robot that irons clothes.

 

Explain two criteria that consumers will evaluate in the clothes ironing robot, before buying one.

2 marks total
1 mark per explanation

Sample answers:
  • Consumers will evaluate the safety of the robot, to make sure it does not contact clothes too long, which would cause a fire.
  • Consumers will evaluate the effectiveness of the robot, to make sure it gets all the wrinkles out of clothes.
  • Consumers will evaluate the efficiency of the robot, to make sure that it completes the task of ironing as quickly as possible, using as little energy as possible.


Question 5
3 marks

For thousands of years, people travelled and transported goods by walking, using horses to pull carts, and by paddling boats. Transportation took a lot of effort, and it took a long time to travel a great distance.

 

Today, we have many transportation machines to travel around the world quickly, such as vehicles, trains, ships, and airplanes. Modern vehicles are powered with fossil fuels such as gasoline, or electricity.



What scientific discoveries and technologies were invented before fast transportation machines could be invented?
Explain one positive way that fast transportation machines have changed people’s lives.
Explain one negative way that fast transportation machines have changed people’s lives.

3 marks total
1 mark per explanation

  • Engines that burn fossil fuels and electric motors were invented before fast transportation machines could be invented.
  • Fast transportation machines allow people and goods to travel much further and faster than they did in the past.
  • Burning fossil fuels in fast transportation machines creates carbon dioxide, which is a greenhouse gas that contributes to climate change.
  • Accept any other reasonable answers.