2. Which of the following two ways of warming your house would be yield the most efficient method of heating:

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1 IDS 101 Energy Transformations End of Module Questions 1. Imagine a remote island that is slightly larger than this campus and that has a well developed plant ecosystem, but no animals. If we introduce 100 mice and 100 cats to the island, what would you predict the population of the mice and cats would be after 10 years? (Assume that the mice eat just the plants, while cats only eat the mice). We are looking for relative answers, such as there will be more than or there will be more (or fewer) than when the were introduced to the island. Provide the reasoning for your answers. Over time the number of organisms that eat only plants will be greater than the predators because there is more energy available for the mice than there is for the cats. To keep mice alive, plant material (grain for example) must be converted to mouse material (muscle for example). To keep the cats alive, plant material must be converted to mouse material which must be converted to cat material. There are more energy transformations required to keep cats alive so more energy is lost along the way and thus the island can support fewer cats. In a natural environment, there will be more rabbits than coyotes, more deer than mountain lions, more mice than hawks because there is less energy available for the predators. (In the question above, it will depend on the success of the mice in escaping the cats it is possible that both groups will not survive if the mice are over hunted). 2. Which of the following two ways of warming your house would be yield the most efficient method of heating: A. You burn 100 pounds of coal in a stove inside your house (the fumes from the burning go out a chimney to the atmosphere). B. The volume of the same type of coal is burned at an electrical power plant and you use the electricity to warm your house. Explain your answer. You will receive more heat from burning the coal directly (alternative A) assuming that the stove has a reasonable thermal efficiency. There would be several energy conversions in the coal-fired electric option, such as the heat that would be lost from the coal-fired plant, the friction of turning a turbine, losses in electricity transmission (we have not discussed this yet!), and the loss of energy in converting the electricity to heat in your home.

2 3. To the right is a photo of an amusement ride at the Puyallup Fair. The ride spins around the central shaft and the floor of the ride move down when the ride spins fast enough. What types of energy transformations occur with this ride? Assume that the source of the energy to drive the ride is electricity. Electricity is the power for the ride. There will be a loss of energy to heat as the wires that transmit the electricity in the machine warm the air around it. There will be friction that releases more heat energy. As the ride rotates, the moving stuff (metal, lights, people, etc) gains kinetic energy. On this ride, the floor drops away as it spins. The force of the rotation pushes people to the outside wall. The force of this push increases the friction between the people and the wall so they do not fall when the floor is lowered. Some of the energy is converted into sound energy (this would not include the people screaming!) Some of the kinetic energy of the ride moves the air around the ride. 4. Sometimes sports trainers use something called a "cold pack" to cool an injury. One type of cool pack has water and ammonium nitrate in separate containers inside the packet. The cool pack is a room temperature, but when the cold pack is shaken, the water and ammonium nitrate combine creating the cold pack. We are not interested in the chemical details of the reaction between water and ammonium nitrate, but what can you say about the energy transformations happening and the flow of energy when the pack become cold? Chemical reactions may absorb heat or release heat. In this case the area around the cold pack becomes cooler so the chemical reaction must absorb heat from the area around it (and from very material of which it is made). B. The opposite type of packet is called a "hand warmer". If you expose the hand warmer to the air or shake the packet, it gets warmer. Describe the flow of energy and the transformations. This chemical reaction must release thermal energy which flows to the area around the hand warmer (such as our hands).

3 5.A The pole vault is a track and field sports event in which a competitor uses a flexible pole to jump over a horizontal bar high in the air. It goes something like this: A pole vaulter begins by standing still and holding the pole level pointing straight in front of her. Then she runs forward gaining speed until she reaches the point of her jump. At that point she jams the end of her pole into the ground. The pole bends as she continues to move forward. As she jumps, the pole straightens, lifting her into the air. She drops the pole as she throws herself over the horizontal bar high the air. She falls down on the far side of the horizontal bar, landing on a soft mat which compresses as she bounces up and down on it several times. List at least five energy transformations that take place in this process. As (write below) is happening the kind of energy known as. is changing to this kind of energy. 1. as she starts to run Chemical energy in her body as she runs 2. as she runs Heat from friction between her shoes and the track 3. as she puts the pole in the box Elastic potential energy in the pole as it is bent 4. as the pole straightens out Elastic potential energy of her motion into the air 5. as she reaches the top of her jump Gravitational potential energy 6. as she falls to the pit Gravitational potential energy as she falls 7. as she impacts the cushion in the pit 8. as the cushion is compressed 9. as the cushion expands again Her kinetic energy turns to... Elastic potential energy in the cushion turns to... Work on the cushion Elastic potential energy in the cushion and... Her kinetic energy and heat and so on and so forth...

4 5B. The following photos are of Old Faithful and the Firehole River in Yellowstone National Park in Wyoming: One of the largest volcanoes in North America is located in northwest Wyoming. Today we call this region Yellowstone National Park. Although there have been no recent historical eruptions in Yellowstone, earthquakes tell us that magmas are still present under the surface. The rocks around the magma chambers are heated by the magmas. Rainfall and snow melt seep into the ground along small fractures and faults. This water is heated by the hot rocks above the magma. As more and more groundwater flows into the fractures, the water at depth becomes very hot and turns to steam. The steam pushes all of the water above it to the surface and the water and steam erupts as you see in the photo of Old Faithful. Some of the water evaporates into the dry Wyoming air and the remainder of the hot water falls to the ground and runs over the surface to the Firehole River increasing the temperature of the water in the river. This increased temperature permits an increase in the amount of biological activity in the river. List at least five energy transformations that take place in this process. As (write below) is happening the kind of energy known as. is changing to this kind of energy. 1. the magma cools Thermal energy in the magma Thermal energy in the surrounding solid rock** 2. as water moves downward through small fractures and opening Friction (heat) since the motion is VERY slow, this energy is minimal. Friction is what causes the slow rate of movement. 3. as the water increases in temperature Thermal energy from the solid rock Thermal energy in the water ** we call this conduction. We have not studied conduction yet, but this is a good example.

5 4. as the water starts to boil Thermal energy from the solid rock 5. as the water converts Potential energy in from a liquid to a gas it superheated water expands 6. water and steam erupt into the air Thermal energy and kinetic energy of the moving water Work changing the water from a liquid to a gas in water moving to the surface Thermal energy in the air 7. as the water reaches the top of the fountain 8. as the water falls to the ground Gravitational potential energy Gravitational potential energy 9. as the water runs over the ground to the river and into the river Thermal energy from the water Thermal energy in the ground and the river 5 C. The following is a scenario of what how some nuclear power plants operate. It goes something like this: Inside of a nuclear reactor is nuclear fuel which decays slowly over time. As the fuel decays, it sends out particles at very high speed. The particles then collide with surrounding water and raise the temperature of the water to the boiling point. As the water then boils, the steam pushes on pistons which then turn wheels. The wheels are attached to electric generators which produce electricity. The electricity then flows through wires to our homes where it lights our electric lamps and heats our electric ovens. List at least five energy transformations that take place in this process. As (write below) is happening the kind of energy known as. is changing to this kind of energy. 1. as the nuclear fuel decays it send out particles at high speed Nuclear potential energy of the particle 2. particles collide with the water and the water increases in temperature of the particle Thermal energy of the water

6 3. as the water starts to boil Thermal energy of the water Work to change the water from a liquid to a gas 4. The steam expands in the molecules of steam Pressure inside of the piston 5. The steam pushes on the turbine in the power plant in the steam to kinetic energy in the gas in the turbine plate 6. movement of the turbine of the spinning turbine Friction and heat 7. electric generator and transmission of electricity Electrical energy Heat and light in our homes