Transcript Machines around us

MACHINES AROUND US
WHAT CAN MACHINES BE USED FOR?
Change the size of a force.
Make things speed up (Accelerate).
Change the direction of a force.
THINK!!
Write three examples of machines you think are:
Force Multipliers
Speed Multipliers
Direction Changers
LEVERS
It is a simple machine that is made of a long rigid object (Timber or Metal rod) and a
pivot (Fulcrum).
TYPES OF LEVERS
First-class Lever
These levers have the fulcrum positioned between the effort and the load
Second-class Lever
These levers have the load positioned between the fulcrum and the effort
Third-class Lever
These levers have the effort positioned between the load and the fulcrum
Load
LOAD
Load
Load
FIRST-CLASS LEVERS
SECOND-CLASS LEVERS
THIRD-CLASS LEVERS
MECHANICAL ADVANTAGE
The mechanical advantage of a machine tells you how much easier the task will be:
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
𝑙𝑜𝑎𝑑
𝑒𝑓𝑓𝑜𝑟𝑡
For when we are using levers this can also be calculated as:
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑒𝑓𝑓𝑜𝑟𝑡 𝑡𝑜 𝑓𝑢𝑙𝑐𝑟𝑢𝑚
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑙𝑜𝑎𝑑 𝑡𝑜 𝑓𝑢𝑙𝑐𝑟𝑢𝑚
If we had a mechanical advantage of 2 this means that:
- lift twice the load that you would normally be able to lift
- use half the force you would have otherwise needed to do a particular task
EXAMPLE
Jess applies an effort of 150N to lift a rock of weight 600N using a long piece of wood as a
lever. Calculate the mechanical advantage of the lever.
Load: 600N
Effort: 150N
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
𝑙𝑜𝑎𝑑
𝑒𝑓𝑓𝑜𝑟𝑡
600
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
150
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 = 4
YOUR TURN
James lifts a 1000N object with a piece of wood, using an effort of 200N. Calculate
the Mechanical Advantage.
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
𝑙𝑜𝑎𝑑
𝑒𝑓𝑓𝑜𝑟𝑡
1000
200
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 = 5
EXAMPLE
Con uses another stick to shift a second rock. The distance from his hand on the stick to
the fulcrum is 120cm. The distance from the fulcrum to the rock is 40cm. Calculate the
mechanical advantage.
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑒𝑓𝑓𝑜𝑟𝑡 𝑡𝑜 𝑓𝑢𝑙𝑐𝑟𝑢𝑚
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑙𝑜𝑎𝑑 𝑡𝑜 𝑓𝑢𝑙𝑐𝑟𝑢𝑚
120
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
40
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 = 3
YOUR TURN
Chloe lifts a box that is 100cm from the fulcrum. Her hand is placed 150cm from the
fulcrum. Calculate the Mechanical advantage.
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑒𝑓𝑓𝑜𝑟𝑡 𝑡𝑜 𝑓𝑢𝑙𝑐𝑟𝑢𝑚
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑙𝑜𝑎𝑑 𝑡𝑜 𝑓𝑢𝑙𝑐𝑟𝑢𝑚
150
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 =
100
𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 = 1.5
QUESTIONS 
Like always answer in your book in silence.
LIST THREE WAYS THAT A MACHINE
CAN MAKE A TASK EASIER?
Question 1
STATE THE UNIT USED TO MEASURE
FORCE
Question 2
A LEVER IS A SIMPLE MACHINE THAT
CAN INCREASE THE EFFORT SUPPLIED TO
GET A JOB DONE.
Question 3. True or False.
IF USING A CROWBAR TO LIFT A TREE
STUMP, THEN THE TREE STUMP IS CALLED
THE EFFORT
Question 4. True or False
A CROWBAR USED AS A LEVER ROTATES
ABOUT A POINT CALLED A FULCRUM
Question 5. True or False
WHEN USING A CLAW HAMMER TO PULL
A NAIL OUT OF A PIECE OF WOOD, THE
HAMMER ACTS AS A FORCE MULTIPLIER
Question 6. True or False
CALCULATE THE SIZE OF THE
MECHANICAL ADVANTAGE FOR THE
SYSTEMS ABOVE
Question 7.
INCLINED PLANES
RAMPS
If we lift an object directly it requires a large effort.
We can use a ramp or inclined plane to make it easier.
We use a smaller force over a longer distance
https://www.youtube.com/watch?v=JL4u89wTnzM
https://www.youtube.com/watch?v=9yFvlcw8YtY
https://www.youtube.com/watch?v=hRyv6b_mGzU
WEDGES
Wedges are used to split objects as they change the direction of a force.
ZIPS
Page 304
Is a combination of 3 wedges. 1 that splits the teeth. 2 that brings the teeth together
SCREWS