Science D

Question 1

The lever

Answer 1

the lever - is a rigid bar or plank that can rotate around a fixed point called a pivot or fulcrum
taks- Are used to reduce the force needed to carry out a task such as pulling a nail, opening a bottle, hitting a baseball, and cutting paper.
advantage- Can move a larger load than you could without using it.
disadvantage- You must move a greater distance than the load does
A first class lever has the fulcrum between the load and the point where the effort is exerted to move the load. (Ex: seesaw)
A second class lever has the load between the effort and the fulcrum. (Ex: wheelbarrow)

A third class lever has the effort between the load and the fulcrum. (Ex: lifting a cup)
example-

Question 2

inclined plane

Answer 2

task- Help move large, heavy objects that are too heavy to lift straight up.
Advantage- Makes it possible to lift heavy objects using a smaller force
Disadvantages- You have to exert the force over a larger distance, compared with lifting the object straight up.
Generally useful only for small inclines.
The steeper the angle of a ramp, the harder it is to control the motion of an object as it moves up or down the ramp.
example- ramp for wheelchair

Question 3

wedge

Answer 3

The wedge machine is forced into an object.
task- You can exert a force so it splits an object apart.
advantage- The wedge increases the force that you apply on the object.
disadvantage- It moves a greater distance into the object than the split it causes
A wedge can be used only in one direction.
example- a knife

Question 4

screw

Answer 4

A screw is a cylinder with a groove cut in a spiral on the outside.
task-a screw helps you increase the force you use
advantage- It can penetrate materials using a relatively small force.
Converts rotational (turning) motion to linear motion (motion in a straight line).
disadvantage- Most screws will move objects very slowly.
example- wine bottle opener

Question 5

pulley

Answer 5

A pulley consists of wire, rope, or cable moving on a grooved wheel.
task- They can be linked together in systems for moving and lifting objects.
advantage- Pulleys help you lift larger loads than you could lift on your own.
disadvantage- Requires a specific set up with ropes that may not be ideal in all situations.
example- in a well

Question 6

wheel and axle

Answer 6

The wheel and axle is a combination of two wheels of different diameters that turn together.
task- A longer motion on the wheel produces a shorter, but more powerful motion at the axle or using a wheel and axle to increase the size of a force.
advantage- wheel and axle can also be used to increase speed
disadvantage- The drawback is that you have to turn a greater distance (a larger wheel) to apply the force
example- door handle, a bike

Question 7

Archimedes screw

Answer 7

this device can move large volumes of water or other substances. Originally it was powered by hand.
His device used a large screw inside a tube. One end of the tube is placed in water. When the screw turns, it raises water up to the top of the tube. Used to be hand-powered, but now uses motors

Question 8

Simple machines can be used to obtain one of the effects below

Answer 8

Changing the direction of a force (for example, a pulley on a flagpole)
Multiplying force (for example, a screwdriver)
Increasing or decreasing speed (for example, scissors)
Transferring force (for example, a staple remover)

Question 9

Sakia

Answer 9

Persian water wheel used animal power to turn a wheel connected to a pulley of buckets that dip into a well.

Question 10

Complex Machine

Answer 10

system in which simple machines all work together; parts of a complex machine that have just one function are called subsystems and often contain a simple machine
complex machine = system

Question 11

Systems & subsystems

Answer 11

subsystem- (of a machine) smaller group of parts within a complex machine that performs a specific function
System: (in context of machine) a group of parts that work together to perform a general function, forming a complex machine

Question 12

Linkage, fan belts, transmission

Answer 12

Linkage- belt or chain to transfer energy from an energy source to an object
Transmission: special type of linkage for transferring the energy from the engine to the wheels in large vehicles such as cars and trucks
Cars- a belt used as a linkage in older car engines-fan belt

Question 13

Gears

Answer 13

consist of a pair of wheels that have teeth that interlink. When they rotate together, one gearwheel transfers turning motion and force to the other. The larger gearwheel rotates more slowly than the smaller gearwheel, but it rotates with a greater force.
Gears control the transfer of energy in the system
work together in gear trains of two or more wheels

Question 14

Driving gear

Answer 14

the gear that has the force applied directly to it from an outside source (your foot).

Question 15

Driven gear

Answer 15

the gear that moves in response to the driven gear.

Question 16

High gear

Answer 16

driving gear is larger than the driven gear.
This leads to a speed advantage. Why?
When the driving gear makes one rotation, the driven gear will make more than one rotation.

Question 17

Low gear

Answer 17

driving gear is smaller than the driven gear.
This leads to a force advantage. Why?
When the driving gear makes one rotation, the driven gear will only make a partial rotation.
Or, you could look at it like this. In order to get one rotation on the driven gear, the driving gear will need to make multiple rotations.

Question 18

Reducing gears

Answer 18

decreases the turning speed in a device. In reducing gears, the driving gear is smaller and has fewer teeth than the driven gear.

Question 19

Change direction

Answer 19

When two gears mesh together, the second one always turns in the opposite direction. So if the first one turns clockwise, the second one must turn counterclockwise.

Question 20

multiplying gear

Answer 20

gear for increasing speed.

increase the speed of rotation in a device

Question 21

Gear train

Answer 21

gear wheels work together in gear trains of two or more wheels. The gear that has a force applied to it from outside the gear train is the driving gear then applied to the driven gear.

Question 22

Calculations of: Mechanical Advantage, Speed Ratio, Efficiency, Work

Answer 22

Mechanical Advantage (MA) = Output force
––––––––––––
Input force
Efficiency = __Mechanical Advantage__ x 100
Speed Ratio
Speed Ratio (SR) = Input distance
Output distance
Work = F ✕ d or W = N ✕ m

Question 23

Units: force, work, distance

Answer 23

force= Newtons (N) Work= Newton Meters (Nm) or Joules (J) distance= meters and centimeters

Question 24

Mechanical advantage

Answer 24

How much a tool strengthens a force
The amount by which a machine can multiply a force
What does that mean?
It means how much it is increasing the effort you put into the machine
Also referred to as the force ratio of the machine
Input Force
The force applied to the machine
Output Force
The force the machine applies to the object
you are determining how much your force is being multiplied by the system in order to complete the task
A high (>2) factor means you gain a HUGE force advantage!
A low (between 1-2) factor means it’s not gaining much force advantage, and the machine is only making it a little easier than just moving something yourself.

Question 25

Speed Ratio

Answer 25

Well, speed measures the distance an object travels in a given amount of time
So the measure of how the speed of the object is affected by a machine is called the speed ratio
A low (between 1-2) factor means you gain a HUGE advantage! You’re moving the object almost equal to what you put into the machine.
A high (>2) factor means it’s not gaining much advantage, and the machine is only moving it a little bit for the greater distance you need to move it yourself.
Calculating the speed ratio is another way of analyzing how machines work.

Question 26

Friction

Answer 26

Friction is a force applied in the opposite direction/resisting force
The smoother the surface the less friction
Mechanical Advantage is affected by friction
Speed Ratio is not affected by friction
Friction means more force is needed to overcome that resistance in order to move an object. Friction also produces heat.

Question 27

Efficiency

Answer 27

Friction is what causes change in efficiency
What is efficiency?
A measurement of how well a machine or device uses energy
Efficiency is a measurement of how well a machine or device uses energy. Is calculated as a Percentage, by dividing the MA by the SR.
The more energy that is “lost”, the less efficient a machine is. (Ex. More rope surface pulling on on a pulley wheel creates more friction, and increases the energy lost.)
Complex machines are very inefficient.
Efficiency can also be calculated using work input and work output.

Question 28

When is work done?

Answer 28

work is done when a force acts on an object to make the object move.
movement is needed before you can say that work has been done.
Without energy, there would be no work done.
the amount of work done depends on two things:
• the amount of force exerted on the object.
• the distance the object moved in the direction of the applied force.

Question 29

Work Calculations

Answer 29

Woutput = F output x d output
Workoutput = 800 N x 2 m = 1600 J
Friction is the reason that work input does not equal work output in real situations. It affects a machine’s efficiency.

Question 30

Newton

Answer 30

The Newton (N) is the unit for measuring force. It is named after Sir Isaac Newton, the great scientist who studied force and motion.

One Newton is equal to the amount of force exerted by Earth’s gravity on a mass of about 100 g (e.g., an egg, an orange).
One Pascal equals the force of 1 newton over an area of 1 m2.

Question 31

Joule

Answer 31

The Newton·metre is called a joule, named after the English scientist James Joule.

Question 32

Explain the phrase “you don’t get something for nothing” when relating to the advantage of simple machines.

Answer 32

Even though you are able to lift a heavier load the trade
off is you have to travel a greater distance in order to do it! you do not get “something for nothing” when you use a machine.
The pulley system in multiplies the force you exert, which is an advantage.
But in using the pulley, you have to pull much farther than the load actually moves.

Question 33

Explain how subsystems work together within complex machines.

Answer 33

Within the bicycle are groups of parts that perform specific functions, such as braking or steering. These groups of parts are called subsystems. The subsystems in a complex machine have just one function each. A subsystem usually contains a simple machine.
All the subsystems work together to complete the task that the complex machine was designed to do. The bicycle is a good example of a complex machine. Several
subsystems work together to move you forward at different speeds, allow you to turn, and help you stop. Each subsystem uses a simple machine to help you do the task more easily. Some of the subsystems in complex machines that produce motion play a role in the transfer of energy or force.

Question 34

Describe how gears are used to increase and decrease speed.

Answer 34

Gears are wheels with teeth that slot together. When one gear is turned the other one turns as well. If the gears are of different sizes, they can be used to increase the power of a turning force. The smaller wheel turns more quickly but with less force, while the bigger one turns more slowly with more force.
Increase speed: If you connect two gears together and the first one has more teeth than the second one (generally that means it’s a bigger-sized wheel), the second one has to turn round much faster to keep up. So this arrangement means the second wheel turns faster than the first one but with less force.
Reducing gears decrease the turning speed in a device. In reducing gears, the driving gear is smaller and
has fewer teeth than the driven gear,

Question 35

What are the input and output forces in a machine?

Answer 35

Input Force
The force applied to the machine

Output Force
The force the machine applies to the object

Question 36

How does friction affect a machine’s efficiency?

Answer 36

Friction affects the mechanical advantage of a mechanical device, so it also affects its efficiency. Any machine, such as a pulley lifting an object, loses some energy as it operates. Usually the energy is lost to heat because of friction.
We say it is “lost” because it isn’t being used directly for the pulley’s task of lifting. It becomes heat, which is not needed or wanted for the task.

Question 37

Why can no machine ever be 100% efficient?

Answer 37

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Question 38

What are the major categories of criteria consumers need to consider before purchasing?
(Evaluating products based on criteria)

Answer 38

• efficiency and effectiveness
• function and design
• Considering the environment

Question 39

Efficiency vs Effectiveness

Answer 39

When you use a mechanical device, you want it to work efficiently. efficiency could be calculated as a percentage by dividing the mechanical advantage by the speed ratio. That’s a quantitative measure efficiency can also be described qualitatively 🡪 quickly and easily

Question 40

Environmental Impact

Answer 40

when buying a mechanical device 🡪 need to think about how to evaluate it🡪 need to consider the environment

Example: spikes in the tires on a mountain bike might make the bike more effective in climbing slopes.

However, tires with spikes would tear up the soil and plants even more than ordinary bike tires do.

Question 41

Evolution of design

Answer 41

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Question 42

Can opener case study

Answer 42

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Question 43

Robots

Answer 43

The word “robot” comes from the Czech word robotnik, meaning “workers” or “slaves” CHANGES IN SOCIETY RESULT IN NEW TECHNOLOGY
example is the use of robots. Robots are widely used today, mainly in industry

Question 44

What are other criteria to consider depending on the product? Ex: shoes, bike, TV, phone?

Answer 44

How long it lasts?

Question 45

Why do designs of products change?

Answer 45

remember 🡪 Each new design was the result of the previous device having
some problem.

Question 46

What was the impact of introducing robots into machinery?

Answer 46

by the middle of the 20th century, people were demanding better wages and better working conditions. As wages went up, industry looked for ways to replace humans in manufacturing and other applications. Robots were the answer.