Kinetic Energy

Steve, Mary, Annie, and James hit four identical tennis balls with a racket. The diagram below shows the top speed at which each tennis ball moved when it was hit.

Based on the diagram, which of the following is true about the tennis balls when they were at their top speed?

• James's ball had the most kinetic energy.

• Steve's ball had the most kinetic energy.

• Mary's ball had the most kinetic energy.

• Annie's ball had the most kinetic energy.

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Kinetic energy is the energy of motion. How could you determine how much kinetic energy an object has?

• by finding its height and width

• by finding its speed and direction

• by finding its position and form

• by finding its mass and speed

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Juniper and her cousins are racing model cars they have built. Based on the table below, whose car has the most kinetic energy as it rolls down the road?

• Kylie

• Craig

• Sheldon

• Juniper

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A pitching machine is used to pitch two balls. The speed of both balls is 94 km/hr.

The mass of one ball is 5 grams, and the mass of the other ball is 50 grams. Since both balls are traveling at the same speed, which of the following is true?

• Neither ball has any kinetic energy.

• The 5-gram ball has more kinetic energy than the 50-gram ball.

• The balls have the same kinetic energy.

• The 50-gram ball has more kinetic energy than the 5-gram ball.

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The diagram below shows two boulders that are rolling down a mountain slope.

The mass of one boulder is 1,000 kilograms, and the mass of the other boulder is 50 kilograms. If both of the boulders are moving at the same speed, which of the following statements is true when both reach point A before touching the ground?

• The 1,000-kg boulder has more kinetic energy than the 50-kg boulder.

• The 50-kg boulder has more kinetic energy than the 1,000-kg boulder.

• Neither boulder has any kinetic energy.

• The boulders have the same kinetic energy.

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A small car is traveling at a speed of 60 mph on the highway. In the next lane, a large passenger bus is traveling at the same speed.

Which of the following is true?

• The car and the bus have potential energy, not kinetic energy.

• The car and bus have the same amount of kinetic energy.

• The car has more kinetic energy than the bus.

• The bus has more kinetic energy than the car.

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NGSS.MS-PS3-1

Two cars that are identical except for their color are traveling on the same road.

The red car is traveling at a speed of 78 km/hr, and the blue car is traveling at a speed of 106 km/hr. Which of the following statements is true?

• Neither car has any kinetic energy.

• The red car has more kinetic energy than the blue car.

• The blue car has more kinetic energy than the red car.

• The cars have the same kinetic energy.

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A graph showing the kinetic energy of a ball over time is shown below.

Which of the following statements best explains the relationship between the kinetic energy of the ball and its speed?

• The kinetic energy of the ball increases over time as the ball travels at a constant speed.

• The kinetic energy of the ball increases as its speed increases.

• The kinetic energy of the ball decreases as its speed increases.

• The kinetic energy of the ball remains the same as its speed increases.

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NGSS.MS-PS3-1

Daniel and Robert went rowing. While Robert was rowing at a speed of 8 km/h, Daniel was rowing at a speed of 10 km/h in the opposite direction.

If the masses of the boats and their rowers are equal, which of the following is a true statement about their kinetic energies?

• Only Robert has kinetic energy because he is rowing in the forward direction.

• Robert has more kinetic energy than Daniel.

• Daniel has more kinetic energy than Robert.

• Only Daniel has kinetic energy because his energy cancels out Robert’s.

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Two motorboats are traveling down a river. Motorboat 1 has a mass of 6,000 kg, and motorboat 2 has a mass of 1,500 kg. The graph below shows the kinetic energies of the boats as they gain speed.

If both boats gain speed at the same rate, why does motorboat 1 have more kinetic energy?

• It sits up higher in the water.

• It has more mass.

• It encounters more air resistance.

• Its length is greater.

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