Simple machines TECHNOLOGY Carles Egusquiza Bueno IES Rocagrossa – Lloret de Mar 1 “Give me a place to stand and I will move the Earth” Simple Machines

Simple machines TECHNOLOGY

Carles Egusquiza Bueno IES Rocagrossa – Lloret de Mar1

“Give me a place to stand and I will move the Earth”

Simple Machines

Archimedes of Syracuse (c. 287 BC – c. 212 BC)



Lever Inclined plane

Unit 1: Force, work and machines



Wheel Screw



Wedge Pulley



When we

we make a

When we

we make a

Lesson 1: FORCE

Letters Word

shup lulp

crefo

push

pull

force

pull

push

force

force



A force is any cause that can...

(1) …increase the speed of an object.

(2) …decrease the speed of an object.

(3) …change the trajectory of an object.

(4) …change the shape of an object.

divert

decelerate

deform

accelerate

A force is any cause that can...

(1) …___________________ an object.

(2) …___________________ an object.

(3) …___________________ an object.

(4) …___________________ an object.

accelerate

decelerate

divertdeform



QUANTITY QUANTITY SYMBOL

UNIT OF MEASUREMENT

UNIT SYMBOL

length l metre m

time t second s

mass m kilogram kg

force F Newton N



Student A &

Student B Student A did half the work of student B

Student B &

Student A

Student C &

Student A

Student D &

Student A

Student B &

Student D

Student C &

Student B

Student B did double the work of student A

Student C did double the work of student A

Student D did four times the work of student A

Student B did half the work of student D

Student C did the same work as student B

Lesson 2: WORK AND ENERGY



The bigger the force, the bigger the work

The longer the distance, the bigger the work

So, mathematically…

Work = Force x distance

W = F x d



ENERGY

MACHINE

WORK

petroltransport

people

food run

electricity phone

windgenerateelectricity



Energy… is the ability to do work.

ENERGY MACHINE WORK



QUANTITY QUANTITY SYMBOL

UNIT OF MEASUREMENT

UNIT SYMBOL

length l metre m

time t second s

mass m kilogram kg

force F Newton N

work W Joule J

energy E Joule J



Problem A

A man ______ a box for ____. To ____ the box, the man _____ a _____ _____. Find the

____ done in the _______.

Problem B

A person _____ a ____ to ____ an object from the floor. The ______ reached is ____ and

the _____ done is ______. Determine the ______ necessary to ____ the object.

Problem C

A _____ _____ is _______ to move a _________ doing ________ of ____ in the _______.

Find the ________ the _________ has been moved.

pushes 10 m move makes 200 N force

work process

pulls rope lift height 15 m

work 4500 J force lift

400 N force applied motorbike 20000 J work process

motorbikedistance



1. A road vehicle with two wheels is a…

2. What’s the name of the distance between the ground and something above it?

3. If you …….. something, you elevate it.

4. It is a thick cord or wire.

5. A ……..……. is a series of actions which are executed in order to achieve a result.

6. A …………… is any cause that can change the movement or the shape of an object.

7. When you move something making a force, you are doing…

8. To use force in order to move something towards you.

9. To use force to make something move away from you.

motorbike

Height

lift

Rope

process

force

work

To pull

To push



W = F x dRemember…

FForce

Unit to measure force: NEWTON (N)

WWork

Unit to measure work: JOULE (J)

dDistance

Unit to measure distance: METRE (m)



Problem A A man pushes a box for 10 m. To move the box, the man makes a 200 N force. Find the work done in the process.

m10·N200d·FW J2000

F = 200 N

d = 10 m



Problem C A 400 N force is applied to move a motorbike doing 20000 J of work in the process. Find the distance the motorbike has been moved.

d·FW F

Wd

m 400

J 20000 m 50

Problem B A person pulls a rope to lift an object from the floor. The height reached is 15 m and the work done is 4500 J. Determine the force necessary to lift the object.

d·FW d

WF

m 15

J 4500 N300



Lesson 3: MACHINES

A 10 26 34 1 24 37

B 33 35 6 27 31

C 36 2 21 19 22 32

a e r o p l a n e A 10 26 34 1 24 37

f r i d g e B 33 35 6 27 31

c o m p u t e r C 36 2 21 19 22 32



D 16 38 12 8

E 15 11 28 40 3 39

F 9

G 13 14

I 20 25 18 30 5 29 7 23

b i c y c l e D 16 38 12 8

v e n t i l a t o r E 15 11 28 40 3 39

d r i l l F 9

b u l l d o z e r G 13 14

t e l e p h o n e I 20 25 18 30 5 29 7 23

H 17 4

c l o c k H 17 4



s 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

s s

19 5 3 20 21 22 23 24 25 26 27 12 28 29

s

30 31 32 33 34 35 2 36 2 37 1 38 39 40 15 40 20 12

What’s a machine?

A m a c h i n e i a n y d e v i c e

t h a t u e e n e r g y t o

p e r f o r m o m e a c t i v i t y



Sentence 1

Usually cars have four wheels but motorbikes and bicycles have just two.

Sentence 2

To get high speed in ski jumping, skiers slide down a ramp or inclined plane.



Sentence 4

Taking water from a well is much easier if you have a rope and a pulley.

Sentence 3

Screws can be used to join pieces but also to make moving devices like a car’s jack.



Sentence 6

A wooden pallet is easier to break if you have a crowbar to use as a lever.

Sentence 5

You can cut logs with a saw or you can split them with a wedge and a sledgehammer.



1. What is a simple machine?

A simple machine is a device that changes the direction or the magnitude of a force.

2. Why are simple machines useful?

Simple machines are useful because they make work easier.

3. How does a simple machine work?

A simple machine works by using a single applied force to do work against a load.

4. How many moving parts has a simple machine got?

A simple machine has got few or no moving parts.

5. Why is learning the basics of simple machines important?

Learning the basics of simple machines is fundamental to understanding more intricate mechanisms.

6. What’s the relationship between simple machines and more complicated machines?

Simple machines can be thought of as building blocks for more complicated machines.



Simple machines

Inclined plane Lever

Screw WedgeWheel

and axlePulley

7. Which are the two basic simple machines?

The two basic simple machines are the inclined plane and the lever.

8. What devices are variants on the inclined plane?

The screw and the wedge are variants on the inclined plane.

9. What devices are variants on the lever?

The wheel and axle and the pulley are variants on the lever.



1) T F In science weight means the same as mass.

2) T F Weight and mass are forces.

3) T F Weight is a force.

4) T F An object with one kilogram mass weighs one kilogram.

5) T F The kilogram is a unit of mass.

6) T F Sometimes the distinction between mass and weight is unimportant.

7) T F Gravity on the Earth is different depending on the country.

Lesson 4: MECHANICAL ADVANTAGE



8) T F The weight of an object is directly proportional to its mass.

9) T F The weight is 10 times greater than the mass.

10) T F It’s easy to understand the difference between mass and weight comparing the same object on different planets.

11) T F On the Moon gravity is stronger than on Earth.

12) T F The mass of an object is the same on the Moon as on Earth.

13) T F The weight of an object is the same on the Moon as on Earth.

14) T F We can know the weight of a mass using Newton’s second law.

15) T F On Earth the weight of a 5 kg mass is 37 N.



a) Conservation of energy principle:

b) Friction:

c) Frictionless system:

d) Ideal machine:

e) Actual machine:

f) Efficiency:

Energy can neither be created nor destroyed; it can only be transformed from one state to another.

Force that makes the relative motion between two objects more difficult .

Ideal system with no friction forces within it.

Theoretical machine in which there is no loss of energy (e.g., because of the friction).

Machine in which there is loss of energy (i.e., real machine)

Is the ratio of energy used by a machine to the useful work the machine has done.



FRAGILE

mb = 280 kg

L

F

mm = 70 kg



FRAGILE

mb = 280 kg

L

F

LLoad we want to move. It’s the weight of the object. It can also be called resistance or output force.


mm

Mass of the man.

Unit to measure mass: KILOGRAM (kg)

FForce we have to apply to move the object. It can also be called effort or input force.


mm = 70 kg

mb

Mass of the object we want to move.

Unit to measure mass: KILOGRAM (kg)



The load L is the weight of the box, so…

g·mL b2s

m 9,81·kg 200 N 9621

If the man hang from the bar to move the box, his weight will be the force F:

g·mF m2s

m 9,81·kg 07 N 686,7

FRAGILE

mb = 280 kg

L

F

mm = 70 kg



FRAGILE

mb = 280 kg

L = 1692 NF = 686,7 N

mm = 70 kg

The man can lift 1692 N (280 kg) applying a force of 686,7 N (70 kg). The force done is a quarter of the force we would need to lift the box without the bar.

The machine (in this case, a lever) multiplied the force of the man by 4. This number is called mechanical advantage (MA).

MA = 4



Mechanical advantage (MA) is…

… the factor by which a machine multiplies the force applied to it.

… the force amplifying effectiveness of a simple machine.

… the ratio of load to effort.

… the ratio of the force exerted by a machine (the output) to the force exerted to the machine (the input).

F

LMA

N 686,7

N 1962

In the example:

= 4



No, simple machines do not multiplying energy but force.

1. Do simple machines multiply energy?FRAGILE

mb = 280 kg

L = 1692 NF = 686,7 N

mm = 70 kg

MA = 4

The input energy of an actual machine is always bigger than its output work. The reason is that in actual machines there is always a loss of energy due to friction. The

efficiency is not 100%.

2. What’s the relationship between the input energy and the output work of an actual machine? Why?

Winput > Woutput

The input energy of an ideal machine is equal to its output work. The reason is that in ideal machines there is no loss of energy due to friction. The efficiency is 100%.

3. What’s the relationship between the input energy and the output work of an ideal machine? Why?

Winput = Woutput



None because no energy is created by simple machines. They just multiply force. The conservation of energy principle cannot be violated.

4. What principle related to energy do simple machines violate? Why?

To get the same energy with less force you have to apply the force over a longer distance.

5. What’s the cost of making less force with a simple machine to get the same energy?

Winput = Woutput

db

dm

In the example, to move the box a short distance (db), the

man had to move the other part of the lever a long

distance (dm).



5. How can we get the mechanical advantage formula?

outputinput d · Ld · F outputinput WW

F

L

d

d

output

input

By applying the conservation of energy principle.

The ratio of distances is equal to the ratio of forces. We call that ratio mechanical advantage.

F

L

d

dMA

output

input



Problem A A man is lifting a cupboard with a simple machine. The mass of the cupboard is mc = 50 kg. To move cupboard, the man makes a 250 N force. Find the mechanical advantage of the machine.

2s

m81,9·kg 50g·mL c N490,5

F

LMA

m 250

N 490,5 1,96

96,1MA



Problem B A person weighing 800 N moves an object with a simple machine using all his weight. The mechanical advantage of the machine is MA = 5. Determine the mass of the object.

MA·FL F

LMA 5·N 800 N4000

g

Lmo g·mL o

2sm

9,81

N 4000 kg407,75

kg 407,75mo



Problem C A car has a 1000 kg mass. We want to move it with a machine able to multiply the force applied 8 times. Calculate the effort we have to do to move the car.

N 25,1226F

2s

m81,9·kg 0100g·mL c N9810

MA

LF

F

LMA

8

N 9810 N25,1226

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Simple machines TECHNOLOGY Carles Egusquiza Bueno IES Rocagrossa – Lloret de Mar 1 “Give me a place to stand and I will move the Earth” Simple Machines