Energy Unit Review

As the cars of a rollercoaster race down a hill, energy transformations take place. Which of the following is true?

• Some energy is destroyed as the car slows down.
• Kinetic energy is stored in the cars as they move downhill.
• Some potential energy is transformed to kinetic energy and other forms of energy.
• The kinetic energy of the cars is equal to the potential energy of the cars.

The following equation illustrates the chemical reaction that occurs in a plant. water + carbon dioxide + light energy = sugar + oxygen Based on the law of conservation of energy, what happened to the light energy in the reaction?

• It was converted into chemical energy stored in the sugar.
• It was changed into oxygen gas.
• It was destroyed.
• It was produced by the plant.

The unit for energy is the joule (J). Anita and her brother Alberto pedal their bicycles up a hill. Suppose that Anita uses 100 J of energy going up the hill. When she stops pedaling and allows her bicycle to coast down the other side of the hill along side Alberto as shown in the illustration below, Anita's bicycle uses 80 J of kinetic energy and generates 20 J of thermal energy from friction. Given the energy transformations that occur with Anita and her bicycle, which of the following statements is true?

• The law of conservation of energy was obeyed.
• The law of conservation of energy does not apply when thermal energy is involved.
• Energy was destroyed as the bicycle coasted.
• Thermal energy was transformed into kinetic energy.

Energy may be transformed from one form to another. What happens during every transformation of energy?

• All the forms of energy remained unchanged.
• Energy is created.
• Energy is conserved.
• Potential energy changes to kinetic energy.

Energy cannot be created or destroyed. In Kevin’s favorite comic book, the superhero has special powers. In one adventure, the superhero must stop an evil villain who threatens to destroy the city with a powerful energy blast. As he confronts the villain, he makes the following claims: 1: "I can create an energy force field to save the city." 2: "I can destroy the energy before it destroys the city." 3: "I can convert all the energy before it can do any harm to the city." 4. "I can absorb all the energy and make it go away" If the superhero must obey the law of conservation of energy, which of the above can he actually do?

• 1
• 2
• 3
• 4

According to the law of conservation of energy, energy may be changed from one form to another but cannot created or destroyed. Which of the following processes best demonstrates this idea of conservation?

• a person cutting down trees in a forest
• a person recycling various materials
• a person using a bulldozer to tear down a building
• a person creating a painting

Energy cannot be created nor destroyed, only changed from one form to another. How does listening to music on a radio obey the law of conservation of energy?

• Electrical energy is converted into other forms of energy, such as sound.
• Electrical energy remains unchanged.
• Sound energy is changed into potential energy.
• Electrical energy is gradually destroyed as the radio plays.

Katrina tried to take pictures with her new digital camera but discovered that its batteries were dead. What happened to the batteries?

• Kinetic energy had been changed into potential energy.
• All their stored energy had been destroyed.
• All the energy stored in the batteries had been transformed.
• Only chemical energy remained stored in the batteries.

Larissa is a very energetic person and has a hard time sitting still in class. One time in math class, her teacher asked Larissa where she got all of her energy. Since Larissa had just studied energy in science class, she knew the correct answer. What answer did Larissa give her math teacher?

• "I just transform it."
• "I create it!"
• "I can get energy anywhere I want."
• "I make energy whenever I need it."

The unit for energy is the joule (J). If the energy content of an object is 1,000 J, but then later it is found to be 900 J, what happened to 100 J of its energy?

• The object absorbed additional energy from its surroundings.
• Energy was created.
• Energy was destroyed.
• The object transferred some of its energy to its surroundings.