Physical Science Final Exam 8th Grade Chapter 8, 9, And Part Of 10

Friction is a force that opposes the motion between two surfaces that are touching. When two objects are in contact and one tries to slide or move over the other, friction comes into play. It acts in the opposite direction to the motion and makes it difficult for the objects to move smoothly. Friction arises due to the roughness of the surfaces and the interlocking of their irregularities. It is an essential force in our daily lives, as it allows us to walk, drive, and hold objects without slipping.

A wheel and axle is a simple machine consisting of two circular objects of different sizes. The larger circular object is called the wheel, while the smaller circular object is called the axle. The axle is attached to the center of the wheel and allows it to rotate. This simple machine is commonly used in various applications, such as vehicles, bicycles, and door knobs, to transfer and amplify rotational motion.

The law of conservation of energy states that energy cannot be created or destroyed, but it can only be transferred or transformed from one form to another. This principle is based on the understanding that energy is a fundamental quantity in the universe and is always conserved in any physical process. It is a fundamental law in physics and has wide-ranging applications in various fields, including mechanics, thermodynamics, and electromagnetism.

Nuclear energy is the correct answer because it is a type of energy that is generated from nuclear reactions. Without the energy from the sun, life on Earth would not be possible as it provides heat and light necessary for various biological processes. Nuclear energy is not directly derived from the sun, but it plays a crucial role in sustaining life on Earth through processes like nuclear fusion in the sun's core.

The term "Mechanical Advantage" refers to a machine's ability to multiply force. It is a measure of how much the machine can increase the input force to produce a greater output force. By comparing the input force with the output force, the mechanical advantage of a machine can be determined. Therefore, the given answer, "Mechanical Advantage," correctly explains the concept of how a machine multiplies force.

Work is done on an object when a force exerted on the object causes it to move in the direction of the force. Work is a measure of the energy transferred to or from an object by means of a force acting on the object. It is calculated by multiplying the magnitude of the force applied to an object by the distance the object moves in the direction of the force.

A pulley is a simple machine that consists of a grooved wheel that holds a rope or a cable. It is used to lift or move heavy objects by changing the direction or magnitude of the force applied. By wrapping the rope around the wheel and axle of the pulley, it allows for easier lifting and pulling of objects. This makes the pulley an efficient tool for tasks that require mechanical advantage.

When one object does work on another, energy is transferred. This is because work is defined as the transfer of energy from one object to another. When an object exerts a force on another object and causes it to move, energy is transferred from the first object to the second object. This transfer of energy allows the second object to gain energy and perform work. Therefore, the correct answer is "transferred."

A machine is a device that can change the size or direction of the force exerted on an object. Machines are designed to make work easier by using mechanical advantage to multiply force or change its direction. They can be simple machines like levers and pulleys, or complex machines like engines and turbines. By utilizing various mechanisms, machines can alter the forces applied to objects, allowing for tasks to be accomplished more efficiently.

When a machine changes the size of a force, the distance must also change. This is because machines work by trading off force for distance. In simple terms, if a machine increases the force applied, the distance over which the force is applied will decrease. Conversely, if a machine decreases the force applied, the distance over which the force is applied will increase. This principle is known as the principle of mechanical advantage and is a fundamental concept in understanding how machines work.

The sun is our most important energy resource because it provides the Earth with heat and light energy through nuclear fusion. Solar energy is renewable and abundant, making it a sustainable source of power. It is harnessed through various technologies such as solar panels and solar thermal systems to generate electricity and heat water. Additionally, the sun's energy is also responsible for driving weather patterns, photosynthesis in plants, and the water cycle, making it crucial for sustaining life on Earth.

A lever is a bar that pivots on a fulcrum, allowing for the amplification of force or the movement of objects. It consists of three main components: the fulcrum, the load, and the effort. By applying force at one end of the lever, the load at the other end can be moved or lifted. Levers are commonly used in various applications, such as seesaws, crowbars, and even human limbs. They are essential tools in mechanics and engineering, providing mechanical advantage and facilitating work.

Geothermal energy is considered a renewable resource because it is derived from the heat generated within the Earth's core. This heat is continuously produced by the natural processes of radioactive decay and the residual heat from the planet's formation. As long as these processes continue, geothermal energy will be available, making it a sustainable and renewable source of energy.

Petroleum and natural gas are considered examples of fossil fuels. Fossil fuels are formed from the remains of ancient plants and animals that were buried and subjected to high pressure and temperature over millions of years. These fuels, such as petroleum and natural gas, are non-renewable resources that release carbon dioxide when burned, contributing to climate change. They are widely used for energy production in various sectors, including transportation, electricity generation, and heating.

The correct answer is the sum of its potential and kinetic energies. Mechanical energy is the energy possessed by an object due to its motion or position. It is the sum of the potential energy, which is the energy stored in an object based on its position or height, and the kinetic energy, which is the energy possessed by an object due to its motion. Therefore, mechanical energy is the combination of these two forms of energy and is not related to the object's mass or the waste energy produced by friction.

The unit for work is Joule. Work is defined as the amount of energy transferred by a force acting through a distance. Joule is the SI unit for energy and work, and it is equal to the work done when a force of one newton is applied over a distance of one meter. Therefore, the correct unit for work is Joule.

The mechanical advantage is calculated by dividing the output force (2,000 N) by the input force (200 N). In this case, 2,000 N divided by 200 N gives a mechanical advantage of 10. This means that the machine amplifies the input force by a factor of 10, allowing the user to exert a greater force on the object.

Chemical energy is the correct answer because sugars and starches in food are broken down during digestion into smaller molecules, releasing energy in the process. This energy is then used by the body to carry out various functions and movements. Additionally, the energy released from the breakdown of these molecules helps to maintain the body's temperature. Therefore, chemical energy is the form of energy that fuels all body functions and movements and helps regulate body temperature.

The given answer "energy conversion" is correct because coal burning power plants convert the chemical energy stored in coal into thermal energy through combustion. This thermal energy is then used to heat water and produce steam, which drives the turbines to generate electrical energy. Therefore, the process involves the conversion of one form of energy (chemical) into another form (thermal and then electrical).

A change in state refers to the transformation of a substance from one physical state to another, such as from solid to liquid or from gas to liquid. This transformation does not involve any alteration in the chemical composition or properties of the substance. Therefore, it is considered a physical change.

Running down the court without a ball is not considered work done on an object because work is defined as the transfer of energy to an object by the application of a force that causes the object to move in the direction of the force. In this case, running down the court without a ball does not involve any force being applied to an object to cause it to move, so no work is being done.

Work input refers to the amount of work that is put into a machine or system. It is the work done on the machine or the energy transferred to the machine in order to perform a task. In the given question, the work done on a machine, such as turning a screwdriver, is referred to as work input.

More efficient light bulbs produce more light energy because they convert a higher percentage of the electrical energy they receive into visible light. This means that less energy is wasted as heat, resulting in a higher output of light energy.

In a closed system such as a roller coaster, all of the mentioned elements are involved. The cars, track, and air are all part of the system and interact with each other. The cars move along the track, which provides the structure and path for the roller coaster. The air also plays a role in the ride, affecting the speed and dynamics of the coaster. Therefore, all of the above options are involved in a closed system like a roller coaster.

The correct answer is geothermal because geysers, including Old Faithful, are powered by geothermal energy. Geothermal energy is generated by heat from the Earth's core, which heats up water and creates steam. This steam builds up pressure underground and eventually erupts through the surface, causing the geyser to erupt. Therefore, geothermal energy is the energy source that powers Old Faithful.

The 100 watt bulb does the most work each second because wattage is a measure of power, which is the rate at which work is done. Therefore, the higher the wattage, the more work is done per second.

The kinetic energy of an object is determined by its speed and mass. Speed refers to how fast the object is moving, while mass refers to the amount of matter the object contains. These two factors play a crucial role in calculating the kinetic energy of an object. As the speed increases, the kinetic energy also increases, while a greater mass results in a higher kinetic energy. Therefore, knowing the speed and mass of an object allows us to accurately determine its kinetic energy.

Burning is not a physical change because it involves a chemical reaction where a substance reacts with oxygen to produce heat, light, and often smoke or ash. Physical changes, on the other hand, do not involve a change in the chemical composition of a substance. Boiling, freezing, and melting are all physical changes because they involve a change in state or phase of matter without altering the chemical composition of the substance.

A block and tackle is an example of a compound machine because it consists of multiple simple machines working together to achieve a mechanical advantage. In this case, the block and tackle system utilizes both the wheel and axle and the lever principles to make lifting heavy objects easier. The wheel and axle allows for the rotation of the pulleys, while the lever principle allows for the distribution of force across multiple ropes and pulleys, resulting in a greater mechanical advantage.

A wedge is a double inclined plane that moves. It is a simple machine with a triangular shape that is used to separate or lift objects by applying force to its thick end. When the wedge is pushed or driven into a material, it creates a split or separation due to its shape and the applied force. This makes it an effective tool for tasks such as splitting wood, cutting through materials, or holding objects in place.

In the solid state, water molecules are tightly packed and have the least amount of freedom to move. This results in lower average kinetic energy compared to the other states. In the gas state, water molecules have the highest average kinetic energy as they are far apart and move freely. In the liquid state, water molecules have intermediate kinetic energy as they are still able to move around but are closer together compared to the gas state.

Gas particles have high kinetic energy and move rapidly in all directions. This constant motion allows them to overcome the attractive forces between particles, resulting in a lack of fixed shape or volume. The fast movement of gas particles leads to their ability to fill any container and diffuse throughout space.

When a bow is stretched, it stores potential energy. Potential energy is the energy that an object possesses due to its position or condition. In this case, the bow is stretched, which means it is in a position where it can potentially release energy when it is released. Therefore, the correct answer is potential energy.

When a machine is used to perform a task, it can cause changes in both the size and the direction of the input force. This means that the force applied to the machine can result in both a change in the size or magnitude of the force, as well as a change in the direction in which the force is applied. Therefore, the correct answer is "Changes in size and direction when done by machine."

Plants use light energy during photosynthesis to produce new substances with chemical energy. Photosynthesis is the process by which plants convert light energy into chemical energy in the form of glucose. This chemical energy is stored in the plant and can be used for various metabolic processes. Therefore, the correct answer is "use light energy to produce new substances with chemical energy."

A machine's mechanical efficiency refers to the ratio of output work to input work, expressed as a percentage. A mechanical efficiency of 95% suggests that the machine is able to convert 95% of the input work into useful output work, with only a small percentage being lost as waste or friction. This indicates a highly efficient machine that is able to perform its intended task with minimal energy loss.

The thermal energy of a substance changes with the kinetic energy of its particles. This is because thermal energy is the total energy of all the particles in a substance, and kinetic energy is the energy associated with the motion of particles. As the particles move faster, their kinetic energy increases, leading to an increase in the thermal energy of the substance. Therefore, the correct answer is kinetic energy.

A light bulb conserves energy by converting some of the electrical energy it receives into both thermal energy and light energy. This means that it does not waste all of the energy it consumes, but instead utilizes it to produce both heat and light. By converting the electrical energy into useful forms, the light bulb is able to be more energy-efficient and conserve energy.

When two substances have the same temperature, it means that their particles have the same amount of thermal energy. This thermal energy is related to the average kinetic temperature of the particles, which refers to the average speed of the particles in the substance. Therefore, if two substances have the same temperature, it implies that their particles have the same average kinetic temperature.

Sound energy is a form of energy that requires a medium such as air, water, or solids to travel through. It cannot travel through a vacuum because a vacuum is an empty space devoid of any particles for sound waves to propagate. Therefore, the given description of sound energy is incorrect.

Inclined planes do not allow you to apply a smaller force over a smaller distance. In fact, inclined planes allow you to apply a smaller force over a longer distance, making it easier to move objects vertically or horizontally. This is because the inclined plane increases the distance over which the force is applied, reducing the amount of force needed to move the object.

Fossil-fuel and nuclear plants use steam to turn a turbine that rotates the generator. In these types of power plants, heat is generated by burning fossil fuels or through a nuclear reaction. This heat is then used to produce steam, which is directed towards the turbine. The high-pressure steam causes the turbine to spin, and as a result, the generator connected to the turbine also rotates, producing electricity. Therefore, steam plays a crucial role in the generation of electricity in fossil-fuel and nuclear plants.

Levers are divided into classes according to the location of the fulcrum, the load, and the input force. This means that the position of these three elements determines the class of the lever.

Anita completes the job twice as fast as Juan, which means she does the same amount of work in half the time. Power is the measure of how quickly work is done, so Anita's actions involve twice as much power compared to Juan.

An electric generator is not an energy resource because it is a device that converts mechanical energy into electrical energy. It does not produce energy itself, but rather transforms energy from another source, such as fossil fuels or renewable sources like wind or water, into electricity. On the other hand, the heat inside the Earth, plant matter, and falling water are all examples of energy resources as they can be harnessed directly to generate power.

When you exert a force on an object and it moves in the direction of the force, work is being done. This is because work is defined as the transfer of energy that occurs when a force is applied to an object and it moves in the direction of the force. In this scenario, the force applied by you causes the object to move, which means that work is being done on the object.

The power is calculated by dividing the work done by the time taken. In this case, the work done is 50 J and the time taken is 5 s. Therefore, the power is 10 W.

Natural gas is considered the cleanest burning fossil fuel because it produces fewer emissions compared to other fossil fuels like coal and oil. When natural gas is burned, it releases lower levels of carbon dioxide, sulfur dioxide, and nitrogen oxide, which are major contributors to air pollution and climate change. Additionally, natural gas combustion produces minimal ash and particulate matter. This makes natural gas a more environmentally friendly option for generating electricity and heating compared to other fossil fuels.

A third-class lever always has a mechanical advantage of less than 1 because the effort arm is shorter than the load arm. In a third-class lever, the effort is applied closer to the fulcrum than the load, resulting in a smaller force being exerted on the load compared to the effort applied. This means that the force output is always less than the force input, resulting in a mechanical advantage of less than 1.

At the top of your jump on a trampoline, your potential energy is at maximum. This is because potential energy is the energy stored in an object due to its position or state. When you are at the highest point of your jump, you have the maximum potential energy because you are furthest away from the ground and have the greatest potential to fall and release that stored energy.