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Science Unit Test 2
| Question | Answer |
|---|---|
| What is the definition of a system? | A group of parts working together to do one job, where each part has its own role. |
| What are the two main types of systems? | Physical and social. |
| What are the two kinds of physical systems? | Natural and human made. |
| What are three kinds of human-made physical systems? Where do the names of these types of systems come from? Provide some examples of each. | Three types: electrical, mechanical, and optical. They’re named after the kind of energy they use to work. |
| What is the purpose of a human-made physical system, generally-speaking? | To make a particular task easier to perform. |
| What are subsystems? | Systems are made of subsystems that work together to do a bigger job. |
| What are natural physical systems? Provide some examples. | Natural physical systems are systems that happen in nature, not made by humans. Some examples are ecosystems, and solar systems. |
| What are social systems? Name some human and non-human social systems. | Social systems are systems made up of living things working together. Human: government, legal system, social groups Non-human: beehive, wolf pack |
| What is a mechanism in a human-made physical system? | A mechanism is a part of a human-made physical system that changes one force into another (i.e., an input force into an output force) |
| What do “inputs” and “outputs” refer to when thinking about human-made physical systems? | Inputs are the forces, raw materials, energy…etc. that are used to produce a particular output or result (i.e., the completion of particular tasks, services, products…etc.) |
| Why are simple machines “simple”? | Because they only have 1 or two parts and use one input force to produce one output force. |
| Name the two families of simple machines as well as the names of 2 types of simple machines from each family (i.e., not specific examples, such as a stapler or an ice auger). | Inclined Plane Family and Lever Family. |
| What is an inclined plane? What are they often used for? | A slanted flat surface. They are often used to raise or lower an object a particular distance. |
| What is a wedge? What are they often used for? | A wedge is a type of inclined plane, its a small, triangle-shaped tool that comes to a point. Its used to split things, lift things, or hold things in place |
| What is a screw? Why is it part of the inclined plane family? What are they used for? | A screw is an inclined plane wrapped around a central metal core. Its an inclined plane because it’s basically a sloped surface twisted around. Its used for turning something to make it move forward or hold things together. |
| What are the three main parts of a lever? | The load arm, the effort arm, and the fulcrum. |
| What are levers used for? | Levers are designed so that the force applied to one part of the lever can be changed or redirected in order to move a load. |
| What is another name for the “load force”? | Resistance. |
| What are the three different classes of lever? What is the defining feature of each type of lever? Provide an example of each. | Class 1 - Fulcrum in the middle, like a teeter totter Class 2 - Load is in the middle, like a wheelbarrow Class 3 - Effort is in the middle, like a set of tongs |
| What is a wheel and axle? Why is it considered part of the lever family? | A wheel and axle is a wheel attached to a stick (axle) that turns together. Its a lever because the axle acts like the bar of a lever, and the point where the wheel turns is the fulcrum. It makes turning things easier using rotary motion. |
| What are gears? Why are they considered to be part of the lever family? | Gears are wheels with teeth that fit together to turn. They’re part of the lever family because the teeth push like a lever, helping one gear move another. |
| What is a gear train? | A gear train is a series of gears that are connected together in a system. |
| What is a pulley? Why are they considered to be part of the lever family? | A pulley uses a wheel and axle apparatus to make lifting or pulling objects easier. |
| How are pulley types identified? | Pulley types are identified by how many pulleys there are - single, double, or multiple and whether they’re attached or not – fixed, movable, or a mix if there’s more than one. |
| What are forces? | Forces are pushes or pulls on objects that results in changes in the movements of those objects. |
| What are the four main types of forces in nature? | Gravitational force, electromagnetic forces, strong nuclear force, weak nuclear force. |
| What is gravitational force? How does it compare to electromagnetic forces in terms of its relative strength? | Gravitational force is the pull that pulls things toward each other (like objects toward Earth) Compared to electromagnetic forces, it’s really weak, so most movement isn’t caused by gravity. |
| What forces are most responsible for movement in our daily life? | Electromagnetic forces |
| What are the 7 types of electromagnetic forces that we learned about in this class? Describe each one. | Rotational - associated with spinning, twisting, and turning Tensile - associated with stretching and tightening; tension Compressive - associated with crushing, squeezing, pressing Magnetic - magnetic pull or push between the poles of magnets; opposit |
| What are the two types of frictional forces? Describe them. | Static frictional force is the friction that exists between two objects that are in contact but are not moving. Sliding frictional force is the friction that exists between two objects that are in contact and are in motion. |
| True or False: Friction only occurs in solids. Explain your answer. | False because frictional forces can occur in and between matter that is in any state (solid, liquid, or gas) |
| What is the relationship between friction and the efficiency of a human-made physical system? | Friction reduces the efficiency of a system by creating heat and wearing down system components. |
| How can the friction in a human-made physical system be reduced? | By using lubricants. |
| All forces have two main characteristics. What are they? | A magnitude (a size) and a direction. |
| What units of measure are used to indicate the magnitude of a force? | Newtons (N) |
| How many Newtons are in Kilonewton? How do you convert between Newtons and Kilonewtons? | There are 1000 Newtons in a Kilonewton (kN). To convert from N to kN, we divide by 1000. To convert from kN to N, we multiply by 1000. |
| What is the difference between mass and weight in science? | Mass – the amount of matter in an object. It doesn’t change no matter where the object is and is measured in grams or kilograms. Weight – the force of gravity acting on that mass. It can change depending on the strength of gravity and is measured in Newto |
| The force of gravity on earth is 9.8 N/kg. The force of gravity on the moon is ⅙ of the force of gravity on Earth. Therefore, the force of gravity on the moon is… | 1.63 N/kg |
| True or False: An input force that is greater than or equal to gravity is required to resist gravity. Explain your answer. | True because If the input force is less than the force of gravity, movement against will not be able to occur |
| What is mechanical advantage? | Mechanical advantage is how much a machine helps you do work. You can figure it out by comparing the force you put in to the force the machine gives out, or the distance you move to the distance the load moves. It shows how much easier a machine makes a |
| If you calculate mechanical advantage and you get a value that is greater than 1, what does that mean? | If the value is greater than one, then it means that the output force is greater than the input force, which means that the simple machine in question has made the job easier than it would have been without it. |
| What units of measure are used for mechanical advantage? Why? | None. This is because it is a ratio. |
| What do you need to know about a system in order to calculate mechanical advantage (note that there is more than one way to calculate mechanical advantage). | You need to know the input distance and output distance or the input force and output force. |
| If you calculate mechanical advantage and you get a value that is less than 1, what does that mean? | It means that the output force is less than the input force. |
| A hockey stick is used to propel a puck down the ice at fast speeds. What is true about the hockey stick? | The mechanical advantage of the hockey stick is less than 1. |
| What is the difference between ideal and actual mechanical advantage? | Ideal mechanical advantage does not take the effects of friction into account, while actual mechanical advantage does. |
| True or False: Ideal and actual mechanical advantage can be calculated using the same mathematical formulas. | True and False, depending. True in that you can use the formula MA = Output Force/Input Force to calculate both. False in that you cannot use input and output distances to determine the actual mechanical advantage. |
| True or False: Ideal mechanical advantage is always greater than actual mechanical advantage. Explain your answer. | True, because friction reduces the mechanical advantage because some of the force put in will always be lost to friction. |
| What is the defeniton for work? | Work is when force is used to move an object a certain distance. |
| What is the scientific definition of “energy”? | Energy is defined as the ability to do work (i.e., use force to move an object) |
| What is the ultimate source of all energy on Earth? | The sun. Energy from the sun is then cycled through the environment (i.e., passed through food chains). |
| True or False: All energy that is put into a system is used to do useful work. Explain your answer. | False because, some energy is always lost from the system via friction, heat, light, vibration…etc. |
| What is the relationship between energy loss from a system and the efficiency of that system? | When energy is lost from a system, it becomes less efficient; as a result, we generally want to manage or reduce energy loss as much as possible to ensure that we’re not wasting energy. |
| How can energy be lost from social systems? Provide some examples. | 1. When there is too much bureaucracy and a task doesn’t occur efficiently because there are too many steps 2. Individuals become sick, stressed or overworked, so it takes them longer to complete a task/time off is required |
| What is efficiency in human-made physical systems? | Efficiency refers to the proportion of input energy that is used to do useful work within a human-made physical system. |
| What units are used to measure efficiency? Why? | Percent (%). This is because we are looking at the portion of input energy that was used to do work and was not lost from the system or wasted. |
| What does it mean when the efficiency of a system is greater than 100%? | It is not possible for a system to be more than 100% efficient. |
| What is a class 1 lever? | When the fulcrum is in the middle. |
| What is a class 2 lever? | When the load is in the middle. |
| What is a class 3 lever? | When the effort is in the middle. |
| What are the 2 families of simple machines? | Inclined plames, and levers. |
| What simple machine fits into the lever family? | Wheel and axle, and a pulley. |
| What simple machine fits into an inclined plane? | Wedge, and screw. |
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