D: Mechanical Systems, section 1 and 2: machines, work, hydraulics Flashcards
What is an Archimedes screw?
A device that can pump fluids upward
What is a simple machine?
A tool or device made up of one basic machine
What are the six basic machines?
Lever Inclined plane Wedge Screw Pulley Wheel and axel
Explain a lever
A ridged bar or plank that can rotate around a fixed point
What are the advantages of a lever?
With a lever you can move a larger load than without using it
What are the disadvantages of a lever?
You have to move a greater distance than the load does for this to work
What is an inclined plane?
A flat surface at an angle to another flat surface
What are the disadvantages of an inclined plane?
- You have to exert force over a longer distance compared to lifting straight up
- generally used for small inclines
What are advantages to an inclined plane?
It makes it possible to to lift heavy objects using small force
What is a wedge?
A simple machine that looks like an inclined plane or a triangle but it is forced into an object.
Examples include knives and door stops.
What are the advantages to an inclined plane?
It increases the force you apply to an object
What are the disadvantages to a wedge?
A wedge can only be used in one direction
What is a screw?
A cylinder with a groove cut in a spiral on the outside
What are the advantages of a screw?
It helps increase the force you use.
It can penetrate materials using relatively small force.
It can also convert turning motion into straight
What are the disadvantages of screws?
Most will move objects very slowly
What is a pulley?
A pulley consist of a wire, rope, or cable moving on a grooved wheel
What are the advantages of a pulley?
They can be linked together and they help you lift larger loads
What are the disadvantages to a pulley?
A pulley requires a long durable rope
What is a wheel and axel?
It is a combination of two wheels of different diameters. A longer motion on the wheel creates shorter but more powerful motion at the axel
What does The acronym ‘EFL the ELF FEL’ mean?
Class 1 lever:
EFL-Effort Fulcrum Load
(Teeter totter)
Class 2 lever:
ELF-Effort Load Fulcrum
(Wheelbarrow)
Class 3 lever:
FEL-Fulcrum Effort Load
(Hockey stick)
What is a machine?
A tool that helps humans do work
What is a hydraulic system?
It uses a liquid under pressure to move loads
What is a complex machine?
A system in which all simple machines work together
What is each part in a complex machine called?
A subsystem
What are subsystems?
They are parts that perform specific functions such as breaking or steering
What is a linkage?
A belt or chain used to transfer energy from an energy source
What is a transmission?
A special type of linkage for transferring the energy from the engine to the wheels in large vehicles
What are gears?
A pair of wheels that have teeth that interlink
Which gear is the driving gear?
The gear that has force applied to it from the outside
What is the driven gear?
The gear that the driving gear applies force to
What is mechanical advantage?
It is the amount which the machine can multiply force
What is input force?
The force applied to the machine
What is output force?
The force the machine applies to an object
What is speed ratio?
A measure of how the speed of an object is affected by a machine
What is friction?
A force that opposes motion
What is efficiency?
A measurement of how well a machine or device uses energy
What is a mechanical system?
A mechanical system is a system that uses mechanical devices to perform tasks.
How many mechanical systems have you used today?
You may have used several mechanical systems without realizing it.
A mechanical system is a set of physical components that convert an input motion and force into a desired output motion and force. Mechanical systems have at least three elements: input, process and output. The input part of the system is any type of motion and force that drives the mechanical system.
What are some examples of tasks that involve mechanical systems?
Riding a bicycle, opening a can, sharpening a pencil.
What is the primary function of mechanical systems?
To help complete tasks that might be difficult to perform otherwise.
What is the energy source in mechanical systems?
Energy can come from electricity, gasoline, solar energy, or human power.
What historical example is given to illustrate human power in mechanical systems?
The construction of huge structures like the pyramids.
What type of energy powers a bicycle?
The energy comes from a pedalling human.
True or False: Machines have not changed significantly as science and technology have evolved.
False.
What will you learn about in this unit?
How small, human-powered mechanical devices work and the principles behind them.
What are some types of mechanical devices you will design and build?
Devices powered by hydraulics and pneumatics.
What principles do simple tools like scissors function on?
The same principles as massive equipment powered by fluid pressure and heat engines.
Fill in the blank: All mechanical systems have an _______.
[energy source]
What will be examined regarding machines in this unit?
How machines have changed with advancements in science and technology.
What type of simple machine do a screwdriver and a teeter-totter represent?
Levers
Both devices act as levers, changing the amount of force needed to move an object.
What is a lever?
A simple machine that changes the amount of force required to move an object
It consists of a bar that rotates around a fixed point.
What is the fixed point around which a lever rotates called?
Fulcrum
The fulcrum supports the lever and is its point of rotation.
What is the term used for the force exerted on a lever to make it move?
Effort force
This term describes the force supplied to any machine to produce an action.
What does the term ‘load’ refer to in the context of levers?
The mass of an object that is moved or lifted by a machine
The load represents the resistance to movement that a machine must overcome.
What is the distance between the fulcrum and the effort force called?
Effort arm
This distance is crucial in determining the mechanical advantage of the lever.
What is the distance between the fulcrum and the load called?
Load arm
This distance also impacts the lever’s mechanical advantage.
What are the three classes of levers?
Class 1, Class 2, Class 3
The class of a lever depends on the position of the effort force, the load, and the fulcrum.
In a Class 1 lever, where is the fulcrum located?
Between the effort and the load
An example of a Class 1 lever is a pair of scissors.
What is an example of a Class 2 lever?
Wheelbarrow
In a Class 2 lever, the load is between the effort and the fulcrum.
What is a defining characteristic of a Class 2 lever?
Exerts a greater force on the load than the effort force
This class of lever is effective in lifting heavy loads.
In a Class 3 lever, where is the effort applied?
Between the fulcrum and the load
An example of a Class 3 lever is a hockey stick.
True or False: In a Class 3 lever, the effort is less than the load.
True
You must exert a greater force on the lever than the lever exerts on the load.
What is the advantage of using a Class 3 lever?
The load can be moved very quickly
This allows for quick movements, such as in sports like hockey.
Fill in the blank: The oars in a rowboat are an example of a _______.
Class 1 lever
The rudder of a sailboat also functions as a Class 1 lever.
What determines the class of a lever?
The position of the effort force, the load, and the fulcrum
Different arrangements lead to different lever classes.
What acts as levers in the human body?
Bones
Bones provide the structure that allows for movement by acting as levers.
What acts as the fulcrum in the body’s lever system?
Joints
Joints are the pivot points around which bones rotate.
What attaches muscles to bones?
Tendons
Tendons are connective tissues that link muscles to bones, facilitating movement.
What happens when a muscle contracts?
The tendon exerts an effort force on the bone
This action allows for movement or lifting of loads.
What can the load in a lever system be?
• Something being lifted or pulled
• Your own body
For example, during a knee bend, the load can be the weight of the body.
What class of levers are most common in the human body?
Class 3 levers
Class 3 levers are characterized by the effort being applied between the fulcrum and the load.
What are the three classes of levers found in the human body?
• Class 1
• Class 2
• Class 3
Each class has different arrangements of effort, load, and fulcrum.
In the example shown in Figure 4.5A, which muscle provides the effort force?
Calf muscle
This example illustrates the calf muscle acting as the effort force in a lever system.
In the example shown in Figure 4.5B, what is the load being lifted?
15 N object
The biceps muscle provides the effort force to lift this load.
In the example shown in Figure 4.5C, what force is the hand pulling with?
30 N
The triceps muscle provides the effort force to pull the rope down.
What is the Space Shuttle Remote Manipulator System commonly known as?
Canadarm
The Canadarm was designed and built in Canada and functions like a human arm.
How does the Canadarm operate its joints?
By gears
The gears turn to move the arms, which resemble levers.
What is one of the primary functions of the Canadarm?
To launch and recover satellites
It helps retrieve satellites from the shuttle’s cargo bay.
What important mission did the Canadarm accomplish?
Repair of the Hubble Space Telescope
The Hubble Space Telescope can see farther and more clearly than ground-based telescopes.
What is the Space Station Mobile Servicing System?
A more complex version of the Canadarm
It assists in assembling and maintaining the International Space Station.
What is the maximum length of the Canadarm when fully extended?
More than 17 m
It is equipped with a smaller two-armed robot for delicate repairs.
Which countries are involved in the planning and assembling of the International Space Station?
Sixteen countries, including Canada, Russia, Japan, and the United States
This collaboration is essential for the construction and operation of the ISS.
What is the difference between mass and weight?
Weight is a force measured in newtons, mass is the amount of material measured in grams or kilograms
Weight is measured with a spring scale or force meter, while mass is measured with a balance.
Fill in the blank: Weight is measured in units called _______.
newtons
Weight is a measure of force.
Fill in the blank: Mass is measured in _______ or kilograms.
grams
Mass quantifies the amount of material in an object.
What is the scientific definition of work?
Work is defined as the product of the force exerted times the distance moved.
Work = Force • Distance
What units are used to measure work in science?
Work is measured in joules (J).
The joule is named after English scientist James Prescott Joule.
How much work is done when a force of 2.0 N is exerted over a distance of 0.6 m?
1.2 J of work is done.
Calculation: W = F • d = 2.0 N • 0.6 m = 1.2 J
If a lever exerts a force of 6.0 N on a brick and moves it a distance of 0.20 m, how much work does it do?
1.2 J of work is done.
Calculation: W = F • d = 6.0 N • 0.20 m = 1.2 J
True or False: Carrying a 40 N backpack down a hallway for 16 m constitutes work in scientific terms.
False.
Although a force is exerted, the movement is horizontal, not in the direction of the force.
What is an inclined plane?
An inclined plane is a ramp or slope that reduces the force needed to lift something.
Inclined planes are also considered simple machines.
What example is given to illustrate the use of an inclined plane?
Olivia uses a board to create a ramp to lift a 50 kg box of camping gear into the back of a truck.
This method reduces the effort needed compared to lifting the box straight up.
What happens when you exert a force on an object but do not move it in the direction of the force?
You do no work on the object according to the scientific definition.
Example: Carrying a backpack horizontally while exerting an upward force.
Fill in the blank: Work is ______ in action.
energy
This highlights the relationship between work and energy in physics.
Who is work measured after?
James Prescott Joule.
The joule, the unit of work, is named in his honor.
What is the mechanical advantage of a branch-lever if an effort force of 500 N is applied to lift a load of 2500 N?
5
Mechanical advantage (MA) is calculated using the formula: MA = Load force / Effort force.
What is the work you do on a machine called?
Input work
Input work refers to the work done by the user on the machine.
What is the work the machine does on the load called?
Output work
Output work refers to the work done by the machine on the load.
True or False: A machine can do more work on the load than the work done on the machine.
False
A machine never does more work on the load than the input work done on it.
Why do we often say that machines make work easier?
They change the size or direction of the force exerted
Machines allow a smaller force to move a larger load, making tasks easier.
Fill in the blank: Mechanical advantage is the comparison of the _______ produced by a machine to the force applied to the machine.
force
Mechanical advantage compares the load force to the effort force.
What happens to the distance you push on the lever when the effort force is small?
The distance is large
A small effort force requires a larger distance to be effective in lifting the load.
What is the formula for calculating mechanical advantage?
MA = Load force / Effort force
This formula helps to determine how much a machine multiplies the input force.
If the load weighs 2100 N and the effort force is 500 N, what is the mechanical advantage?
4.2
Calculated as MA = 2100 N / 500 N.
In a situation where a person can lift a small car a distance of one meter, what does this represent in terms of work?
About the same amount of work as climbing five flights of stairs
Both scenarios require similar amounts of work despite the different forces involved.
What is the mechanical advantage of a branch-lever if it exerts a force 5 times greater than the force applied?
5
A mechanical advantage greater than 1 allows for easier movement of a large load with a smaller effort force.
What is the formula for calculating mechanical advantage?
Mechanical Advantage (MA) = Load force (F) / Effort force (FE)
This formula helps determine the efficiency of a machine.
What is the mechanical advantage of a bicycle if the effort force is 736 N and the load force is 81 N?
0.11
This indicates that the bicycle has a mechanical advantage less than 1.
What is the mechanical advantage of a pulley on a flagpole if the effort force and load force are both 120 N?
1
A mechanical advantage of 1 indicates that the machine does not change the amount of effort needed.
True or False: A machine with a mechanical advantage less than 1 makes lifting tasks easier.
False
A mechanical advantage less than 1 means that more effort is required to lift a load.
What happens to the direction of the force when using certain machines?
The direction of the force changes
For example, pulling down on a cord raises the blinds.
Fill in the blank: When the effort force and load are equal, the mechanical advantage is _______.
1
This indicates that the machine does not provide any advantage in terms of force.
What advantage does a bicycle provide if it has a mechanical advantage less than 1?
It causes the tire to turn faster than the pedals
This results in the bicycle moving faster than the pedaling speed.
List examples of devices that have a mechanical advantage of 1.
- Pulley systems
- Simple levers
- Inclined planes
These devices do not change the amount of force needed to lift a load.
What is a common misconception about machines with mechanical advantages less than 1?
They make lifting tasks easier
In reality, they require more effort to lift the same load.
What is the mechanical advantage of a lever when the load is less than the effort force?
Less than 1
A mechanical advantage of less than 1 indicates that the effort force exceeds the load force.
What happens to the effort required to lift a boulder as you move closer to the fulcrum?
It becomes harder to lift
The fulcrum is the pivot point of the lever.
How does the length of the effort arm affect the effort needed to lift a load?
The longer the effort arm, the less effort required
A longer effort arm provides a mechanical advantage.
What is the formula for calculating mechanical advantage (MA) of levers?
MA = Load force (FL) / Effort force (FE)
This formula demonstrates the relationship between load and effort forces.
If the effort arm is 3 m and the load arm is 0.3 m, what is the mechanical advantage?
10
MA = Effort arm / Load arm = 3 m / 0.3 m = 10.
What type of lever is a branch used as a Class 1 lever?
It multiplies the effort force by 10
Class 1 levers have the fulcrum between the effort and the load.
True or False: The mechanical advantage of tweezers is greater than 1.
False
Tweezers generally operate with a mechanical advantage less than 1.
What is a characteristic of microsurgery tools used in keyhole surgery?
They require a small incision
These tools allow surgeons to perform delicate tasks through minimal openings.
Fill in the blank: Work is calculated as _______.
Force Distance
This equation reflects the trade-off between distance and force in mechanical advantage.
What technology do surgeons use to see during keyhole surgery?
A television screen connected to a tiny camera
This allows for visualization of the surgery being performed inside the body.
What is the mechanical advantage of Class 1 levers?
Class 1 levers can increase your effort force.
This allows you to lift very heavy objects with minimal force.
What is the main advantage of Class 3 levers?
Class 3 levers move the load a greater distance and at a faster speed.
This is why they are used in activities like hitting a hockey puck.
Define speed in the context of motion.
Speed is the rate of motion or the rate at which an object changes position.
How does the structure of levers in the human body benefit movement?
It allows for the performance of delicate tasks with precision and major tasks requiring speed and flexibility.
What is the mechanical advantage of most levers in the human body?
Most levers have a mechanical advantage smaller than 1.
In terms of effort force, what must muscles usually do with levers in the body?
Muscles usually have to exert a greater force on the lever than the lever can exert on the load.
Fill in the blank: The triceps muscle produces _______ to create rapid hand movement.
a small contraction
What materials are suggested for designing an experiment to test Class 3 lever speed advantage?
Simple materials such as marbles and a ruler.
What steps should be included when designing an experiment related to Class 3 levers?
Write a hypothesis and outline the steps to test it.
What variable would you manipulate in the experiment related to Class 3 levers?
The variable related to the lever’s configuration or load.
How would you measure the speed and distance in the Class 3 lever experiment?
By timing the movement and measuring the distance traveled.
What is the science of designing machines to suit people called?
Ergonomics
Ergonomics comes from the Greek words ‘ergon’ meaning ‘work’ and ‘nomos’ meaning ‘natural laws’.
What factors are taken into account when designing products in ergonomics?
- Body weight
- Height
- Size
- Age
- Gender
These factors ensure the product fits the user comfortably and safely.
What are some examples of products that industrial designers might work on?
- Cars
- Office furniture
- Light switches
These products are designed to be comfortable and safe for users.
Why is ergonomics especially important in work environments?
Occupational safety
Ergonomics helps prevent workplace disorders and injuries.
What is carpal tunnel syndrome?
A common workplace disorder causing numbness and pain in the thumb and first three fingers
It results from repetitive finger movements, often at a computer keyboard.
What causes carpal tunnel syndrome?
Irritated tendons that swell and squeeze the nerve inside the carpal tunnel
This irritation is often due to repetitive movements.
What is a common treatment for carpal tunnel syndrome?
A brace that holds the wrist straight
This prevents irritation of the tissues near the carpal tunnel.
True or False: Carpal tunnel syndrome can cause permanent damage if not treated promptly.
True
Severe pain can extend as far as the shoulder if the condition worsens.
Fill in the blank: To avoid carpal tunnel syndrome, one can operate the computer using a _______.
special pen-like device
This device helps keep the wrist flat while using the computer.
What are ‘pain pilots’?
Hand-held computers that operate using a pen-like device
They are pioneering an approach to reduce wrist strain.
What technological advancement is being developed to further reduce carpal tunnel syndrome?
Voice-activated computer programs
These programs allow operation of computers without the need for a keyboard.
What challenges might an ergonomist face when designing for the International Space Station?
- Cramped positions
- Weightlessness
Ergonomists must ensure comfort and safety in unique working conditions.
What type of machine can provide a mechanical advantage to move a heavy load?
Various machines such as winches, gears, and pulleys
These machines allow for moving heavy loads with smaller effort forces.
What is a winch?
A device consisting of a small cylinder and a crank or handle used to lift loads
It operates by turning the wheel, which helps in moving heavy objects like boats.
In a winch, what does the axle act like?
A fulcrum
The axle is held in place and allows the handle to turn, similar to how a lever operates.
What is the relationship between the handle and the radius of the wheel in a winch?
The handle acts like the effort arm of a lever and is much longer than the radius of the wheel
This allows for a smaller effort force to lift a larger load.
How does exerting a force on the handle of a winch relate to using a lever?
It is similar to applying effort on a lever
The continuous turning of the handle allows for repeated application of force.
Fill in the blank: The force that the cable exerts on the wheel of a winch is like the _______ on a lever.
Load
This analogy illustrates how winches function similarly to levers.
What are some examples of devices that function like winches?
- Manual pencil sharpener
- Reel on a fishing rod
Both of these devices utilize similar mechanical principles as a winch.
True or False: A winch allows for lifting a load without the need for a long lever.
True
A winch effectively shortens the lever while maintaining the ability to lift heavy loads.
What is a wheel-and-axle device?
A device that consists of two turning objects attached at their centers, where one causes the other to turn.
Examples include a winch and various machines with multiple wheel-and-axle combinations.
True or False: The wheel in a wheel-and-axle device must always be round.
False
The ‘wheel’ does not have to be round as long as it meets the criteria of the device.
What advantage does a wheel-and-axle device provide?
Mechanical advantage
Similar to a lever, it helps in performing tasks with less effort.
Fill in the blank: A wheel-and-axle device can generate _______.
speed
This is one of the benefits of using such devices, alongside mechanical advantage.
What type of force do wheel-and-axle devices require?
Large effort force
These devices produce a smaller force on the load in return.
What can be observed in Figure 4.14A regarding the tricycle’s pedals?
The effort force is exerted on the wheel
The clown in the example benefits from the mechanical advantage provided by the wheel-and-axle system.
Identify one benefit of using a wheel-and-axle device over a lever.
Convenience for certain tasks
Wheel-and-axle devices may be more suitable for specific applications than levers.
What is a common characteristic of wheel-and-axle combinations?
They come in a variety of shapes and sizes
This diversity allows for different applications in machines and tools.
What is a wheel-and-axle device used for?
It provides speed for a race car zooming around a track.
What happens when a wheel and axle are attached to each other?
Each makes the same number of rotations every second.
How can you make one wheel rotate faster than another?
By using gears.
What is a gear?
A rotating wheel-like object with teeth around its rim.
What is a group of two or more gears called?
A gear train.
What is the first gear in a gear train called?
The driving gear or driver.
What is the second gear in a gear train called?
The driven gear or follower.
Fill in the blank: The teeth of one gear fit into the teeth of _______.
[another gear]
What causes the second gear in a gear train to turn?
The teeth of the first gear push on the teeth of the second gear.
True or False: A gear train can consist of just one gear.
False
What can gears help you do?
They can assist in various mechanical applications.
What type of mechanical device features sprockets and belts?
A combine.
What is illustrated in Figures 4.17 and 4.18?
Two applications of gears.
Can one gear turn another gear without touching it?
Yes, through a chain connection
What is a gear with teeth that fit into the links of a chain called?
Sprocket
When gears in contact turn, in which direction do they rotate relative to each other?
Opposite directions
When sprockets are connected by a chain, in which direction do they rotate relative to each other?
Same direction
If the front sprocket has 45 teeth and the back sprocket has 15 teeth, how many turns does the back sprocket make for each turn of the front sprocket?
Three full turns
What is the relationship between the speed of rotations of a smaller gear and a larger gear called?
Speed ratio
What is the formula for calculating speed ratio?
Speed ratio = Number of driver gear teeth / Number of follower gear teeth
In the context of bicycle gears, what does a speed ratio of 3 indicate?
The back sprocket makes three turns for every one turn of the front sprocket
Fill in the blank: Each link of a bicycle chain moves the same distance in the same _______.
Period of time
True or False: The distance moved by the front sprocket and the back sprocket can be different.
False
What is the primary function of a chain in a bicycle gear system?
To connect the front gear to the rear wheel gear
What is a pulley?
A grooved wheel with a rope or chain running along the groove
Pulleys are used to lift weights safely and comfortably.
How is a pulley similar to a Class 1 lever?
It has an axle that acts like a fulcrum, with effort arm and load arm
Both systems allow for force direction change.
What are the two types of pulleys?
Fixed pulleys and movable pulleys
Each type has distinct applications and mechanisms.
What is a fixed pulley?
A pulley that is attached to something that does not move
Examples include a ceiling, wall, or tree.
What is the function of a fixed pulley?
It changes the direction of an effort force
Allows for lifting without climbing.
What is a movable pulley?
A pulley that is attached to something close, often by a rope that goes around the pulley itself
This type can be lifted and lowered by pulling on the rope.
Fill in the blank: A single fixed pulley simply changes the direction of the _______.
motion
True or False: A single fixed pulley can make certain movements more convenient.
True
What is an example of a fixed pulley in use?
The pulley used at the top of a flagpole
It allows for raising and lowering the flag without climbing.
How does a movable pulley allow for lifting?
By pulling on the rope attached to the pulley
The load may be attached to the center of the pulley.
How can a pulley be compared to a lever?
A pulley can be compared to a lever, but the ‘effort’ arm and ‘load’ arm are the same length.
What is the primary benefit of using a single pulley?
A single pulley makes lifting a load more convenient.
What is a combination of fixed and movable pulleys called?
A block and tackle.
What is the mechanical advantage of a block and tackle dependent on?
The number of pulleys used.
What is a key feature of pulley systems designed for heavy loads?
They have long cables running around several pulleys.
Fill in the blank: A compound pulley is made up of several pulleys working _______.
[together]
What investigation can help determine the mechanical advantage of a compound pulley?
Performing a specific investigation as suggested in the content.
True or False: A block and tackle can provide a large mechanical advantage.
True.
What does ‘MA’ stand for in the context of pulleys?
Mechanical Advantage.
What type of system is used in an oil pump to raise and lower the pump valves?
A system using several pulleys and a lever.
How can a pulley be compared to a lever?
A pulley can be compared to a lever, but the ‘effort’ arm and ‘load’ arm are the same length.
What is the primary benefit of using a single pulley?
A single pulley makes lifting a load more convenient.
What is a combination of fixed and movable pulleys called?
A block and tackle.
What is the mechanical advantage of a block and tackle dependent on?
The number of pulleys used.
What is a key feature of pulley systems designed for heavy loads?
They have long cables running around several pulleys.
Fill in the blank: A compound pulley is made up of several pulleys working _______.
[together]
What investigation can help determine the mechanical advantage of a compound pulley?
Performing a specific investigation as suggested in the content.
True or False: A block and tackle can provide a large mechanical advantage.
True.
What does ‘MA’ stand for in the context of pulleys?
Mechanical Advantage.
What type of system is used in an oil pump to raise and lower the pump valves?
A system using several pulleys and a lever.
