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D. Structures and Mechanisms · Machines and Mechanisms

Machines and Mechanisms: Unit Review

A1.1 A1.2 A1.3 A1.4 A1.5 A2.1 A2.2 A3.1 A3.2 A3.3 D1.1 D1.2 D2.1 D2.2 D2.3 D2.4 D2.5About 40 minutes
Learning goals
  • I can describe machines and the parts and purposes of their mechanisms.
  • I can describe kinds of motion and how mechanisms transmit and transform motion.
  • I can explain how pulleys, gears, chains and belts change direction, speed and force.
  • I can assess the impacts of machines on people and on the environment.

Words to know

mechanism
The group of moving parts inside a machine that work together.
rotary motion
Turning round and round.
mesh
When gear teeth fit together so one gear turns the other.
mechanical advantage
How many times a machine multiplies your force.
transform
To change motion into a different kind, plane, speed or direction.
impact
A helpful or harmful effect.

Let's review!

In this unit you looked inside machines. You found their parts and purposes, named four kinds of motion, built pulley systems, predicted which way gears turn, counted teeth to work out speed, met mechanisms that change the kind and plane of motion, measured how machines change forces, assessed machines' impacts on communities and the environment, and designed your own lifting machine. This review has a few questions from every lesson. Try each one, then press Show answer to check. If a part feels tricky, go back to that lesson for more practice.

meshing gearsOPPOSITEchainSAMEcrossed beltOPPOSITEWhich way does the follower turn?
Direction rules to remember: meshing gears and a crossed belt make the follower turn the opposite way. A chain (or an open belt) keeps both wheels turning the same way.
bigger forcesmall pushbig liftchange directionpull download upmore speedfast bladehands
Three ways machines change forces: a lever makes a small push into a big lift, a fixed pulley changes the direction, and a hockey stick turns a small hand movement into fast blade speed.

Machines All Around Us

1

What is a mechanism?

2

Describe the purpose of a snowplow.

3

Is a can opener a simple machine or a complex machine? Why?

Mechanisms and Their Parts

1

On a bicycle, name the input and the output.

2

What is the purpose of a crank?

3

What is the purpose of the spring in a clothespin?

Four Kinds of Motion and How Mechanisms Pass Them Along

1

Name the motion: a sewing machine needle; a clock pendulum; a ceiling fan.

2

What does transmit mean?

3

Name two mechanisms that transmit rotary motion.

Pulley Systems: Changing Direction and Force

1

A load needs 70 N to lift by hand. About how much force with a movable pulley that has 2 rope sections?

2

A block and tackle has 4 rope sections. To lift the load 3 m, about how much rope do you pull?

3

What does a single fixed pulley change?

Gears: Teeth That Mesh

1

Two gears mesh. The driver turns counterclockwise. Which way does the follower turn?

2

Five gears are in a row. Gear 1 turns clockwise. Which way does gear 4 turn?

3

What is an idler gear for?

Changing Speed with Gears, Chains and Belts

1

A 48-tooth driver turns a 12-tooth follower once. How many times does the follower turn?

2

A 10-tooth gear turns a 40-tooth gear. Is the big gear faster or slower? What is gained?

3

A crossed belt joins two pulleys. The first turns clockwise. Which way does the second turn?

4

A 36-tooth chainring and a 12-tooth sprocket. How many wheel turns for 2 pedal turns?

Changing the Kind and Plane of Motion

1

Which mechanism changes rotary motion into linear motion, like in car steering?

2

What does a cam do to its follower?

3

Name a mechanism that changes the plane of motion.

How Machines Change Forces

1

A lever lifts a 90 N load with a 30 N push. What is the mechanical advantage?

2

Why does a long gentle ramp need less force than a short steep one? What is the trade-off?

3

Name a machine that gives more speed at the end but needs more force.

Machines in People's Daily Lives

1

Give one helpful impact and one problem of a combine harvester.

2

What is automation? Name one effect it has on jobs.

3

How does an Inuit bow drill change motion?

Comparing Machines: Effects on the Environment

1

Name three criteria for comparing the environmental impact of machines.

2

Which has the smaller impact for mixing batter: a hand egg beater or an electric mixer? Why?

3

Score a rake and a gas leaf blower on noise and air pollution (3 = best, 1 = worst).

Design Challenge: Build a Machine That Lifts

1

Name the steps of the engineering design process.

2

Your winch lifts the load but lets it fall when you let go. Which criterion failed, and how could you fix it?

3

How could you make your lifting machine need less force?

Just for fun

Why did the lever do so well on the unit review?

It had lots of support from its fulcrum!

How to use this review

  • Do the review in two short sittings if your child gets tired. Each section matches one lesson.
  • Keep a few real objects nearby (a bike, a hand egg beater, a spool, jar lids) so your child can show answers.
  • For gear and pulley questions, encourage drawing a quick sketch and counting.
  • Ask "How do you know?" A strong answer names the mechanism and says what it changes: the kind of motion, the direction, the speed or the force.
  • Note which section had mistakes and revisit that lesson.
Check your understanding

Quiz

1.

The moving parts inside a machine that work together are called...

2.

A playground swing shows which kind of motion?

3.

A movable pulley with 2 rope sections lifts an 80 N load. About how much force is needed?

4.

Three gears are meshed in a row. The first turns clockwise. The third turns...

5.

A 30-tooth gear turns a 10-tooth gear once. The 10-tooth gear turns...

6.

A small gear turning a big gear makes the big gear turn...

7.

Which mechanism turns rotary motion into up-and-down motion?

8.

A lever lifts a 100 N rock with a 25 N push. Its mechanical advantage is...

9.

Which machine has the smallest environmental impact for clearing a small walkway of snow?

10.

In the engineering design process, after you test you...

For parents and teachers

Use mistakes to choose what to revisit. Each review section matches one lesson.

  • Can't explain what a machine or mechanism is, or describes looks instead of purpose: revisit Machines All Around Us.
  • Mixes up input and output, or names parts without purposes: revisit Mechanisms and Their Parts and do the mechanism detective activity again.
  • Mixes up reciprocating and oscillating, or transmit and transform: revisit Four Kinds of Motion and How Mechanisms Pass Them Along.
  • Thinks a fixed pulley reduces force, or can't use rope sections to predict force: revisit Pulley Systems: Changing Direction and Force.
  • Gets gear directions wrong, or thinks size changes direction: revisit Gears: Teeth That Mesh and the cardboard gears.
  • Can't count teeth to find turns, or thinks the bigger gear is faster: revisit Changing Speed with Gears, Chains and Belts.
  • Confuses rack and pinion, cam and bevel gears, or doesn't understand plane of motion: revisit Changing the Kind and Plane of Motion and the cam toy.
  • Thinks machines reduce work for free, or can't find mechanical advantage: revisit How Machines Change Forces and the rubber band force meter.
  • Lists only good or only bad impacts, or forgets Indigenous technologies or jobs: revisit Machines in People's Daily Lives.
  • Compares machines using different criteria, or thinks electric means no impact: revisit Comparing Machines: Effects on the Environment.
  • Changes many things at once or skips testing: revisit Design Challenge: Build a Machine That Lifts.

A few mistakes are normal. Praise answers that name a mechanism and explain what it changes (kind of motion, direction, speed or force), careful counting, and thoughtful judgements with reasons.