Question

Please HELP Reading: Chapter 15

1. A car is going down a hill and is also slowing down as it approaches a stop sign. How is the car’s potential energy changing? How is the car’s kinetic energy changing? To what other form does energy go? Explain your answers.

2. Which has the greater amount of internal energy, an iceberg or a cup of hot coffee? Defend your answer.

3. Consider two glasses, one filled with water and the other half full, with the water in the two glasses being at the same temperature. In which glass are the water molecules moving faster? In which is there greater internal energy? In which will more heat be required to increase the temperature by 1◦C? Explain.

4. If the specific heat of water were less, would a nice hot bath be a longer or a shorter experience? Explain.

Answer 1

1) when the car is going down the hill that it has zero potential energy because it in is motion now but yeah we can also say its potential energy will be less when it finally stops because potential energy decreases with decrease in height, when the car is going down and is slowing down then its kinetic energy is decreasing since kinetic energy is directly proportional to velocity, so a decrease in speed will result in lower kinetic energy. when the car gets in motion from the top the potential energy is converted to kinetic energy and when at the stop sign the car stops then its kinetic energy is converted to potential energy, this is due conservation of energy principle and some of the kinetic energy is lost as heat to due application of brakes and work done by the engine.

2) an iceberg will have a greater amount of internal energy , its because the sheer size of an iceberg, its so huge that its mass its significantly higher than a cup of coffee., so it means it has a lot of molecules with energy in them even tho it is cold but its bigger size with greater mass leads to higher internal energy.

3) the molecules in both the glass are moving at the same speed because their speed is not dependent whether the glass is half full or fully full, it only depends on temperature and they both have same temperature so same speed.

the glass with full glass of water will have more internal energy because there are more water molecules so greater is the mass and hence greater energy

again since the full glass has more water molecules than the half full one , so the heat required by the fully filled will be higher to heat more water molecules.

4) specific heat tells us that how much heat anything can hold , so if the specific heat of water were less than it means that a hot tub of water wont be able to stay heated a longer period of time so it will be a shorter experience because the water will cool down quickly.