Unit 4 Mechanical Systems Section 1.0 Machines are tools that help humans do work. Define: machine- 1.1 Simple Machines- Meeting Human Needs Water Systems Then: Now: The earliest devices were devices. Each machine was designed to meet needs. They all had one thing in common, they all depended on or for their source of. 1. 2. Main Components: Parts of a Roman Aqueduct: 1. How is gravity used to maintain pressure? 2. 3. Two methods used to raise water levels: 1. Two examples of the Archimedes screw in use today: 1. 2. 2. Define: simple machine-
Complete the following table of the six simple machines: (The advantage and disadvantage columns will be filled in together as a class when we are going over the worksheet) Simple Machine and Description Advantages Disadvantages Example **General Rule: If you have an effort force advantage, you have a disadvantage. If you have a speed and distance advantage, you have an disadvantage.
Name the three different classes of levers, describe how each looks using the terms: fulcrum, load force, and effort force, draw a diagram to illustrate each and give two examples of each. i) - Examples: ii) - Examples: iii) - Examples:
Look at the diagram at the top of page 262. If A is 10 times the distance of B from the fulcrum, the person will use of the force needed to move the object without a lever. Effects obtained by simple machines Do Check and Reflect- p. 268- #1, 2, 4
1.2 The Complex Machine- A Mechanical Team Complex machine - System - Subsystems - Use the bicycle to explain the terms complex machine, system and subsystems. Read Give It a Try- p. 271 and answer the three questions about the pencil sharpener. Name and Describe two subsystems that transfer forces:
Read research p. 273. Ask your parents, or a friend to help you answer the questions about automatic and manual transmissions. Define GEAR WHEEL: Define GEAR: 1. Gears can be used to: 2. 3. 4. Gears are important in mechanical systems because they control the of in the system. 6. 7. 8. 9. Define GEAR TRAIN: The gear that applies 10. the force is: 11. Gears are important in mechanical systems because they control the of in the system. 12. a) Define: The gear that moves as a result of the force is: gear train-
Complete the statements: a) If the gear is larger than the gear, the turning speed of the system increases, and are called gears. b) If the gear is smaller than the gear, the turning speed of the system decreases, and are called gears. In a ten-speed bicycle: a) the driving gears are found at the and the driven gears are found at the. b) when you are in first gear, the gear is large and the gear is small. c) when you are in tenth gear, the driving gear is and the driven gear is. d) first gear can be described as a (multiplying reducing) gear system. e) tenth gear can be described as a (multiplying, reducing) gear system. Which gear would you use to: i) pedal up a very steep hill? ii) pedal down a stretch of very flat highway? Do Check and Reflect- p. 276- #2, 3-a,b Do Assess Your Learning- p. 277- #1, 2, 4, 5-a,b
Section 2.0- An understanding of mechanical advantage and work helps in determining the efficiency of machines. 2.1 Machines Make Work Easier Read Infobit, p. 279. a) What simple machine is being incorporated into the construction of the road up the mountain? b) Talk to your parents, friends of the family or research for yourself. Can you find any other places that show this simple machine being used within the construction of a highway/roadway? Force Definition: Unit: Symbol: Named after: One newton is equal to the amount of force exerted by earth s gravity on g or kg. Mechanical Advantage mechanical advantage- Definitions speed- Speed / Speed Ratio input force- speed ratio- output force- In the car, on p. 279, the force is the force applied by the person and the force is the force applied to the car. The force is larger than the force. Define: input distance- output distance-
Mechanical Advantage Calculations: Speed / Speed Ratio In order to calculate mechanical advantage, you need to know the and, both of which are in newtons. Formula: Mechanical advantage = To be able to calculate the speed ratio, you must know the distance and the distance. Formula: Speed ratio = OR OR M.A. = S.R. = Calculate the mechanical advantage when it takes 30 N of force to lift a 300 N object. Calculate the speed ratio when an object is lifted 2 m by a pulley system and the rope was pulled 10 m. When the mechanical advantage is greater than 1, the input force is (more, less) than the output force. When the mechanical advantage is less than 1, the input force is (more, less) than the output force. When the mechanical advantage is less than 1, the machine is useful for tasks that don t require a. Read the fourth paragraph from the top, on page 282, about the mechanical advantage of a bicycle. Is the bicycle a useful machine? Explain why. A speed ratio of 4 means that the force moves times faster than the force. Read Less force but greater distance, and then calculate the speed ratio for each ramp. Ramp 1 Ramp 2
Mechanical Advantage Speed / Speed Ratio Friction: Define When moving an object with a simple machine, the (input, output) force includes the force necessary to move the object and the force needed to overcome. The speed ratio represents the mechanical advantage, because does not affect its calculation. This means that the theoretical mechanical advantage will be (less, more) than the real or actual mechanical advantage. Affected by friction? Yes No Yes No Why or why not? Why or why not? Friction in a mechanical system results in a need for (more, less) input force, and also creates. The heat comes from the two surfaces against each other and can be reduced by using.
Mechanical Advantage Efficiency Speed / Speed Ratio Define: In any machine some of the energy is lost to, therefore it is not directly used for the task. The more energy that is lost, the less a machine is. Efficiency is calculated as a. Calculations: Formula: Efficiency = OR Efficiency = Calculate the efficiency of a pulley that has a mechanical advantage of 4 and a speed ratio of 5. Because of in the of complex machines, they are often very inefficient. Explain why the efficiency of a typical automobile engine is so low. Do Check and Reflect - p. 286- #1, 2, 3, 4, 5
2.2 The Science of Work Define: work- Work Work Input / Output Define: work input- Is work being done in each of these situations? Explain why or why not. i) Figure 2-10, p. 288 - ii) Figure 2-9a, p. 287 - work output- Read Figure 2.12. In the car, energy from provides a force that makes the different parts of the car to move together causing the car s to move. Calculations: Formula: Work = Formulas: Work input = OR Work output = Work = In the above formula, the force is in units called and the distance is in units called. 90 N 200 N 12 m 3 m The unit of work is the, which is called a. The amount of work done depends on two factors. They are: Using the diagram above as a reference: Calculate the work input when 90 N of force moves an object 12 m. i) ii)
Calculate the amount of work that is done when a force of 80 N is used to lift an object 3 m. 90 N 200 N 12 m 3 m For a bicycle, is being done because your provides a force which is applied to the pedals causing the bicycle to over a distance. Using the same diagram above as a reference: Calculate the work output when a 200 N object is lifted 3 m. Do you think the work input and the work output will be equal most of the time? Read P. 292. Efficiency Efficiency can be calculated another way, using work input and output: Efficiency: Calculate the efficiency for the ramp/inclined shown above. Do Check and Reflect - page 292- #2, 6, 7, 8 & 9
2.3 The Big Movers- Hydraulics Hydraulic System- Define: Before hydraulics were invented, how were construction projects done? Give two examples to illustrate this. Give four examples of where hydraulics are used today. 1. 2. 3. 4. Pressure Definition: Formula: Pressure = or P = Unit: Symbol: Larger Unit: Symbol: Pascal s Law states that. Pascal s Law explains why these two types of systems work. Hydraulic systems use and pneumatic systems use.
A common application of Pascal s Law is the, which is used to In hydraulic systems, the pressure is created by using a, which moves inside of a, and it either fluid out of the cylinder or it fluid into it. Hydraulics and Pascal s Law The pressure on the piston is equal to the pressure created by the piston. Hydraulic devices use a combination of pistons attached to either end of a or flexible pipe. The piston that the force is applied to is the piston and the pressure is transferred to the other piston- the piston. Calculate the mechanical advantage of a hydraulic system which looks like the one on p. 298. The force on the input piston is 30 N and the force of the outward piston is 600 N. The reason for the large mechanical advantage in a hydraulic system is The force and area at each piston, as ratios, have to be. Pascal s Law Pressure large = Pressure small which is the same as Force large = Force small Area large Area small Using the formula above, calculate what the force on the large piston would be if the large piston has an area of 50 cm 2 and the small piston has a 40 N force applied to an area of 10 cm 2. In simple machines, the mechanical advantage comes at a cost. That cost is: Do Check and Reflect- p. 300- # 2, 4 Do Assess Your Learning- p. 303- # 2, 3, 4, 5, 6
Section 3.0 Science, society, and the environment are all important in the development of mechanical devices and other technology. 3.1 Evaluating Mechanical Devices When manufacturers evaluate a device they make, what types of criteria might they use in this evaluation? Name five. i) ii) iii) iv) v) Read Using Criteria to Evaluate a Device. List the criteria that might be important to someone wanting to buy a bicycle. Efficiency: What s the difference between Effectiveness: Define: Function- Design-
Explain what this means. An important aspect of evaluating mechanical devices is ensuring that the design suits the function. Using the bicycles in Figure 3.3, answer the following: a) The primary or main use of the bicycle on the left is b) The primary or main use of the bicycle on the right is Complete the table of design features for bicycles, by stating how each is different and the reason for the change for each type of bicycle. Design Feature Cross-Country Bicycle Road Racing Bicycle Reason Tires Frame Handle bars Three reasons for doing a thorough evaluation of a mechanical device are: a) b) c)
The effect of a device on the environment should also be considered in evaluating a device. Give two examples of this being done from p. 308. As you read through the sections on pop can openers (P. 310-311), complete the table below. Opener Design Advantages Disadvantages Church Key Removable Tab Top Buttons Non-removable Tab Top Read research - p. 312. a) What do the letters CSA stand for? b) What is the CSA? c) Are there any other organizations that test devices for safety and value? If there are, name some of them. Do Check and Reflect - p. 314- #2, 3, & 4.
3.2 Technology Develops Through Change The changes in the pop can opener resulted from both and needs. Also new and contributed to its development as well as new of making the cans. Look at the sewing machines on page 315. Compare the original and the second machine What changes were made? Compare the second and the third machine Why? Read Infobit- p. 315. a) What device was developed that is still in use in vehicles today? b) What was the purpose of this invention and how has it been changed today? Explain how each of these resulted in a new technology. Advances in science, specifically advances in electrical knowledge. (p. 316) Research in particle physics and the use of particle accelerators. (p. 316-317) New technology that results from changes to human society. (p. 317) Changes in the environment result in new technology. (p. 319)
The purpose for creating robots was to A very simple robot contains some, or all of these basic parts. Name them. i) ii) iii) iv) v) vi) Read Careers and Profits, p. 320. What did Peter Robertson invent and why was it an important invention? Name and draw the head of the three most common screws used today. Do Check and Reflect - p. 320- #1, 2, 3 Do Assess Your Learning - p. 321- # 2, 3, 4 Do Focus on Science And Technology- # 2, 3 Do Unit Review- p. 325- # 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 18, 19, 21, 23, 24, 25