Unit 2A Potential, Kinetic and Thermal Energy

A hot pack is a product that releases heat when chemicals inside of it interact. What is taking place

inside an active hot pack?

• electric current

• a net loss of mass

• thermal insulation

• an exothermic reaction

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A type of cold pack has two separate sections inside. One section contains a liquid and the other section

contains a powder. When the cold pack is squeezed, the section that holds the liquid breaks. When the

liquid combines with the powder, the pack becomes very cold.

Which is the best explanation why the temperature of the pack decreases when the liquid and powder

combine?

• A mixture forms.

• A solution forms.

• A chemical change occurs.

• Thermal energy is used.

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Doug builds a model roller coaster with three hills, as shown in the diagram:

He places a toy car at the top of the hill and releases it. The car stops at point X. Which change to the

model would allow the toy car to travel over all three hills?

• Add a loop before the first hill in order to maximize the kinetic energy of the car.

• Add a loop after the tallest hill in order to maximize the kinetic energy of the car.

• Order the three hills from shortest to tallest so that the potential energy builds up according

  to the height of each hill.

• Order the three hills from tallest to shortest to provide the potential energy needed for the

  car to make it over each hill.

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A dump truck, a sports car, and a bicycle are traveling at the same velocity. Which is true?

• They all have the same kinetic energy.

• The sports car has the most kinetic energy.

• The bicycle has the least kinetic energy.

• More information is needed to compare their kinetic energy.

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Which has kinetic energy?

• a tank of gasoline

• a moving car

• a battery

• water in a reservoir

When sodium hydroxide reacts with a copper nitrate solution, the reaction vessel needs to be kept on ice

to slow down the reaction. What best describes this reaction?

• an exothermic reaction that absorbs energy

• an exothermic reaction that releases energy

• an endothermic reaction that absorbs energy

• an endothermic reaction that releases energy

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Mrs. Pearson’s class is studying the amount of energy stored in objects. If the same rock is put in four

different places, at which location will the rock have the most potential energy?

• 
• 
• 
• 

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• As the speed increases, the distance traveled increases as well because there is more kinetic energy present in the system.

• As the speed increases, the distance traveled decreases because there is less kinetic energy present in the system.

• The kinetic energy is the same at the different speeds so the distance traveled does no change.

• There is no relationship.

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Braking distance is the distance a car travels from the time a person applies the brakes to when the car

comes to a complete stop. The graph shows the relationships between the speed of a car and the

distance the car travels before it stops.

Based on the graph, describe the relationship between the car’s braking distance and kinetic energy. Be

sure to use evidence from the graph to support your answer.

• As the speed of the car increases, the braking distance decreases because there is less kinetic energy to turn into potential energy in the system.

• As the speed of the car increase, the braking distance increases because there is more kinetic energy to convert into potential energy.

• As the speed of the car increases, there is no change in the braking distance because the kinetic energy present in the system does not change.

• As the speed of the car increases, the braking distance increases because the potential energy has to convert to kinetic energy.

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Katie conducted three trials of rolling a 5-kilogram ball down 10 steps at her school. Later, her class

used the data she collected about the mass of the ball, the height of the stairs, and the gravitational

constant to calculate the potential energy of the ball. The graph shows the students’ calculations for the

ball at each step of the stairway.

Create a claim about how kinetic energy and potential energy can change as a ball rolls down a set of

steps using evidence from the graph.

• The ball starts at the top of the steps with the most potential energy. As the ball rolls down kinetic energy increases and potential energy goes down.

• The ball starts at the top of the steps with the most kinetic energy. As the ball rolls down the potential energy increases and the kinetic energy goes down.

• The ball starts at the top of the steps with the least potential energy. As the ball rolls down, both kinetic and potential energy increase.

• The ball starts at the top of the steps with the least potential energy. As the ball rolls down, the kinetic energy increases and the potential energy stays the same.

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