While playing at the park, Erica and her sister take turns going down the slide and playing on the swings.
Which of the following is an example of change that is caused by applying energy?

• Erica continues to swing back and forth without trying
• When Erica pushes her sister, her sister slides down the slide
• Erica sits at the top of the slide and waits for her sister to finish her turn
• When Erica stops pushing her sister on the swings, the swing eventually comes to a stop

Alex threw a stick in a river and watched as the river carried it away. He scooped a pail of water from the river and noticed that a leaf was floating in the pail without moving on the surface of the water.
Why did the stick move in the river and the leaf stay still in the pail if it was all the same water?

• The river water cooled off and lost energy when Alex scooped it up into the pail
• There is more water in the river than in the pail so the river could move the stick
• The water in the river has enough energy to move the stick since it is flowing downhill
• Wind could push the stick on the river but could not get to the leaf protected in the pail

When people want to use water to create electricity they generally build a dam to hold the water back, creating a large lake behind the dam.
Why is it necessary to hold the water back with a dam in order to produce electricity?

• It increases the amount of water available
• It increases the force with which the water flows
• It forces the water to flow in the desired direction
• It makes the water still enough to create electricity

If Maria wants to have the best chance of blowing out all of the birthday candles on her birthday cake, she should bend down close to the candles, take a deep breath, make a small opening with her lips and then push her breath out.
Why does doing it this way work the best?

• It keeps the air she breathed in cool enough to put out the candle flames
• It makes the air come out with enough force to blow out the candle flames
• The air forms a blanket over the candles and pushes the candle flames down
• The air spins around when it comes out and hits all the candle flames this way

Todd can throw a baseball from the outfield all the way back to home plate.
Why does he have to move his arm in order to make the ball fly all that way?

• He has to get the ball high enough in the air so the air can support it
• The ball's energy can only be released if he lets it go above the ground
• Moving his arm makes the ball's own energy take it in the right direction
• He has to transfer some of his muscle's energy to the ball to make it move

It is possible to power a small light bulb using a simple battery. Which of the following explains what is happening in the picture?

• Light energy in the bulb is changed to electrical energy in the battery
• Electrical energy from the battery is changed to light and heat energy
• Heat energy from the light bulb is changed to mechanical energy in the battery
• Electrical energy in the battery is changed to mechanical energy in the light bulb

Jennifer is getting ready for school on a cold day in February. She wants to make sure her hair is completely dry before she leaves her house. She plugs her hair dryer into the wall outlet and turns it on.  
Which of the following describes one of the steps involved in using energy to dry Jennifer's hair?

• Thermal energy is changed into mechanical energy, which makes the motor in the hair dryer move.
• Electrical energy is changed into heat energy, which makes the motor in the hair dryer move.
• Mechanical energy is changed into heat energy, which makes the motor in the hair dryer move.
• Electrical energy is changed into mechanical energy, which makes the motor in the hair dryer move.

Shondra was trying to water the flowers with the hose, but even with the water turned up to full force she could not get it to reach the farthest flowers. Her sister told her to cover part of the end of the hose mouth with her thumb. When she did this, the water shot out farther.  
Why did putting her thumb over the end of the hose make a difference?

• The thinner stream of water could travel farther because it was lighter
• Shondra added more energy to the water by making it swirl inside the hose
• The same amount of energy in the water was forced through a smaller space
• The warmth of Shondra's thumb increased the amount of energy in the water

1)  Eric had papers spread all over his table while he was working on a project. When the air conditioner came on several of the papers slid off the table and fell to the floor.
What is the most likely explanation of why the papers moved when the air conditioner came on, and not before?

• The cooler air sank and took the papers along with it
• The fan added enough energy to the air to push the papers
• The air conditioner motor made the floor and the table shake
• As dampness in the papers dried, they could slide more easily

Amy has new rollerskates. She knows that if she stands very still on a flat part of the road with her rollerskates on, she will not move. She has to give a push with her foot in order to start moving.
What else would cause her rollerskates to start rolling?

• getting pushed by a strong gust of wind
• setting the rollerskates in the Sun to warm
• standing on one foot on the flat part of the road
• smoothing the surfaces of the rollerskate wheels