UNIT4. MACHINES
KEY WORD: Simple and compound machines.
BOOK UNIT Nº12: "INNOVATION":
* How does it works?
1. MACHINES.
Leonardo da Vinci was a famous painter and inventor. He lived 500 years ago, but you can still see his creations today. You can see his paintings in museums, but you can also see his inventions everywhere! LIKE HIS MACHINES: bicycle, parachute, submarine and the compass.
MACHINES are devices tha allow you to work easier, better and faster. They help you save time and energy.
We use machines every day. Some machines can be dangerous: you can cut yourself with a sharp knife, you can burn yourself with the cooker, you can get an electric shock from touching a plug.
Here are some of they features:
a) SIMPLES MACHINES have one or few parts. The work with one movement. For example of simple machines: WHEEL, PULLEY, LEVER, RAMP, ...that you can find in objects like: a hammer, scissors, etc.
SIMPLE MACHINES(PDF)
Remember: In a LEVER:
Effort*Distance=Load*distance
b) COMPOUND MACHINES are made up of two or more simple machines working together: motors, gears, electric circuits. For example: a car, a airplane,
a) Machines have many USES, for example: Exerting force, Carring heavy objects, Comunicating, Travelling, etc.
b) HOW THEY WORK. Machines need energy in order to function. The energy comes from different sources: people, electricity, combustible fuels, wind, etc.
ACTIVITIES Nº1:
1.- Name there machines with one or few parts, and three machines with many parts. well, sccisors and hammer / bicycle, car and plane
2.- What machines do you see in the situation of a hospital. X rays machine, tension machine, vital screen, OR lamps, medical special beds, etc.
3.- Name three objects that contain simple machines and three with compoud machines. bike, well, train / car, computer, plane
4.- Find out how many simple machines are combined in a wheelbarrow. wheel, axle and lever
5. Complete the sentences:
- a) Machines are objects that help us to work esier
- b) Planes and cars are compound machines.
- c) All machines need the human being to function.
6. Complete a sentences of these objtects where you describe the energy that they use for.
- a) vacuum we use a vacuum to aspire the dirt
- b) helicopter we use an helicopter to move by the air
- c) stapler we use a strapler to stapl papers
7. You should always take care when using machines. Think of these machines that you can use and write how the canbe dangerous and give a safety rule.
- a) Knives: We can cut ourself. We shouln´t play with them.
- b) plug:you can electrify yourself
- c) jigsaw:you can cut yourself
- d) pistol glue:you can burn your finger
- e) drill: you can drill yourself
8. What sort of SIMPLE MACHINES are these objects?:
- a baseball bat : leaver
- the front of a ship : leaver
- the fan blades : leaver
- a toilet paper dispenser : leaver
- a door knob : leaver
- a broom : leaver
9. Find out the MACHINES that these objects got:
- Stapler: a)leaver b) wedge c) wheel
- Wheel barrow: a) wheel b)axe c) leaver
TASKS:
1.- VIDEO ACTIVITY.
- a) Write in one sentence what the teacher in the video is trying to explain.
- b) What are the simplest of all machines based on?
- c)What type of work is put in a machine?
- d) Archimedes said: “Give me a ………fulcrum……….. and I will ………move………... the …………Earth………”
- e) Which force is bigger in a lever?
EXERCICIES:
1.- Calculate the work requerided to lift a weight of 1200Newton (force) to heigth 9m
1200x9=10800N
2.- A person pushes a suitcase across a railway station for 20m. It the total work performed is 1200Julios, How much force had to be applied?
1200x20=24000N
3.- What category do the following levers belong to? Explain your answer:
a) Screedriver used to open a can, Type 3 b) Fishing pole, Type 2 c) Bicycle brake (hand)Type 3, d) Balance.Type 1
4.- If the drive wheel turns in a clockwise direction, in what direction will the final componet turn? Anticlockwise
5.- To be able to adjust to different slopes and speeds may bicycles have multiple gears.
a) How many different combinations can be used (teeth). (Cassett/Chainring) (pinón/plato). 47/48 teeth, 4 chainring and 2 plato
48/20 48/18 48/16 48/14 44/20 44/18 44/16 44/14
Chainring\Cassett_____ XL - L - M - S.
Larger_L
Smaller_s
b) If the rider goes to 5rpm with the pedals..what speed takes the biky.
5x8/20=12rpm
5x44/14=15.7rpm
5x44/20=11rpm
6.- The pulley for a washing machine drum measures 45cm. in diameter and the motor´s pulley is 9cm in diameter. Calculate the gear ratio and the drum´s speed when the motor is turning at 450rpm.
V1xD2=V2xD2450X9=v2x45
V2= 450x9/45= 90rpm
10.- A mechanism is which the drive gear turns at 200rpm and the driven gear turns at 50rpm:
a) What is the gear ratio.
b) Is the drive gear has 20 teeth, how much has the driven gear.
11.- A force of 300N is required to lift a stone.
a) How much force must be applicaed, if you have a lever with the fulcrum situated at 1m of the stone.
EXERCICIES:
A) LEVERS1.
