Grade 4 Science Practice Test: Energy, Waves and Earth's Surface

The higher the starting point, the farther the cup moved (6, then 13, then 19 cm). A ball released from higher up is moving faster at the bottom, and a faster object has more energy to pass on to the cup.

Batteries store energy. Closing the switch lets an electric current carry that energy through the wires to the bulb, which gives it off as light and some heat. Energy is never made out of nothing; it only moves from place to place or changes form.

Before the collision, only the rolling marble had energy of motion. In the collision some of that energy went to the second marble and some became sound and a little heat, which is why the first marble slowed down. The air carries the sound to your ears, but the energy came from the rolling marble.

Amplitude is how far a wave rises above its resting level, and Wave A's crests are about twice as tall as Wave B's. Wavelength is the distance from one crest to the next: Wave A fits two crests into the same space where Wave B fits four, so Wave A's wavelength is longer.

The duck rises and falls as each wave passes, but it does not travel along with the wave. This shows that a wave carries energy from place to place, while the water itself mostly moves up and down.

A book does not make its own light. Sunlight bounces (reflects) off the book, and some of that light travels into your eyes. Your eyes do not send out light, which is why you cannot see the book in a completely dark room.

A cactus stores water in its thick stem, and the waxy coating slows down the loss of water into the dry air. Large, thin leaves would let water escape quickly, which is why most cacti have spines instead of broad leaves.

The ears are sense organs that pick up the sound. Nerves carry the message to the brain, which makes sense of it and sends signals to the leg muscles to run. The brain cannot react to the sound until the ears have sensed it.

In layers that have not been disturbed, the bottom layers formed first and are the oldest. The lower layers hold fossils of land plants and the top layer holds seashells, so the area was land first and was covered by water later. The opposite story would need the seashell fossils at the bottom.

The bare hill lost four times as much soil as the grassy hill (140 g compared with 35 g). Grass roots hold the soil together and the plants slow down the flowing water, which reduces erosion. Some soil still washed off Hill 1, so the grass did not stop erosion completely.

Coal formed from plants that were buried and squeezed for millions of years. People burn it far faster than nature can make more, so once it is used up it cannot be replaced in our lifetimes. Wind and sunlight are renewable because nature keeps supplying them.

A building in an earthquake zone must hold up during strong shaking. Model 2, with cross braces, was still standing at level 6, while the other two failed at levels 1 and 2. Model 3's heavy roof on thin posts actually made it the first model to fail.