7th Gr Practice Test Unit 2 1-6

When you wave your hands in the air, what happens to the kinetic energy of the air molecules?

• It increases.

• It decreases.

• It stays the same.

Choose the best answer that explains why a guitar stops vibrating.

• As the guitar string vibrates, thermal energy gets converted to KE. The KE transfers energy to the air in the form of sound energy.

• As the guitar string vibrates, kinetic energy gets converted to GE. The GE transfers energy to the air in the form of sound energy.

• As the guitar string vibrates, elastic energy gets converted to KE. The KE transfers energy to the air in the form of sound energy.

The graph shows the average speed of the cars on four different track sections of a roller coaster.  All the cars, when fully loaded with people, have roughly the same mass. Use the graph to answer: Why do the cars in each track section have different amounts of kinetic energy?

• The cars have different amounts of kinetic energy because they have a different amount of mass.

• The cars have different amounts of kinetic energy because they are being driven by different people.

• The cars have different amounts of kinetic energy because they are moving at different speeds.

• The cars all have the same amount of kinetic energy because they are the same type of cars.

The graph shows the average speed of the cars on four different track sections of a roller coaster.  All the cars, when fully loaded with people, have roughly the same mass. Use the graph to answer: Which track has the least and most amount of kinetic energy?

• Track 1 has the greatest kinetic energy because it is first and track 4 has the least amount of kinetic energy because it is last. The mass of the cars is the same.

• Track 2 has the greatest amount of kinetic energy because it is moving the fastest and track 4 has the least amount of kinetic energy because it is moving the slowest. The mass of the cars is the same.

• The cars all have the same mass so they have the same amount of kinetic energy.

• Track 3 is the average speed of the cars so it has the most kinetic energy and track 4 has the least because it is the slowest.

How can the car’s kinetic energy be increased?

• We can increase the car’s kinetic energy by increasing the mass or/and speed of the car.

• We can give the cars a push before they start to move to increase their kinetic energy.

• We can increase the car’s kinetic energy by increasing the size of its’ wheels.

• Once an amount of kinetic energy is set we can not increase it or decrease it.

How does speed affect the amount of kinetic energy in a moving object?

• Speed had no effect on the kinetic energy of a moving object.

• An increase in speed increases the kinetic energy of a moving object because we saw the clay become more compacted.

• An increase in speed only made the clay more compacted, it did not affect the amount of kinetic energy of an object.

• We could not measure the speed of the object so we are unable to measure the amount of kinetic energy of the clay.

How does the energy compare when the skateboarder is on the bottom of the ramp versus when the skateboarder is in the air performing a trick?

• The skateboarder has less gravitational energy on the bottom and more kinetic energy in the air.

• The skateboarder has more gravitational energy on the bottom and less in the air.

• The skateboarder has more kinetic energy on the bottom and more gravitational energy in the air.

• The skateboarder has less kinetic energy on the bottom and more kinetic energy in the air.

Miranda observes her little sister swing on a swing set. She develops a model based on her observations of how gravitational energy and kinetic energy change. Which pie charts would best describe how much gravitational energy and kinetic energy the swing has at each point. 

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 Hydropower plants are a type of hydroelectric plant. Here are some steps in the process of generating electricity for these types of plants.  

Energy is stored in water found in reservoirs located at low elevations.  

The water is pumped to higher elevations. 

The water is then released and then falls due to gravity.

Falling water enables turbines to turn, increasing energy and generating an electrical current.

Which change would decrease the amount of potential energy in the hydropower plant system?

• Increasing the capacity of the reservoir.

• Increasing the length of time the water is stored in the reservoir.

• Decreasing the amount of water falling onto the turbines.

• Decreasing the height between the reservoir and the location where the water is released.

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Nathan placed four books of different masses on a bookcase. How would he arrange the books to show the greatest gravitational energy when only one book is on each shelf? 

• No matter how the books are placed on the shelves, their gravitational energy will remain the same.

• He can place the books from the greatest mass to the least mass from the top of the bookshelf to the bottom.

• He can place the books from greatest mass to least mass from the bottom of the bookshelf to the top. 

• He can place the greatest mass book at the top and the next greatest on the bottom. The middle shelves don’t matter as much as the top and the bottom.