Video Transcript
Which of the following is not true
about the function of gravity? (A) It keeps the hydrosphere’s
position on Earth. (B) It keeps objects and organisms
on Earth’s surface. (C) It is important for the
stability of living organisms when moving. (D) It has no effect on the
atmosphere.
The question mentions gravity. Gravity is a force which attracts
or pulls objects towards the center of the Earth. Everything on Earth which has mass
is pulled towards the center of the Earth. If we think about all the things on
Earth which are pulled by gravity, we must first think of all the things that have
mass. Do land, soil, and rocks have
mass? Yes, gravity acts on these. What about the seas, lakes, and
rivers? Yes, all water bodies have
mass. We call all the water bodies on
Earth, as well as water under the ground and in the atmosphere, the hydrosphere. The hydrosphere is the total amount
of water on a planet, including water on the surface, under the ground, and in the
air.
Gravity holds seas, oceans, and
rivers in place. It also holds water in the air from
floating off into space. Statement (A), it keeps the
hydrosphere’s position on Earth, is true. We can rule out this answer as we
are asked for the statement which is not true.
All living organisms have mass. Gravity also pulls on all living
organisms and keeps them and us from drifting off into space. Also, all nonliving objects have
mass and are held by gravity. So statement (B) is true. It keeps objects and organisms on
Earth’s surface.
Not only that, but the bodies of
all organisms function best under the influence of the gravity of our planet. For example, our muscles have
sufficient strength to move our bodies even though gravity pulls us towards the
Earth every day. If there was no gravity, we could
not run, walk, or move normally. We need gravity to use our bodies
as we do. We can rule out answer (C). It is important for the stability
of living organisms when moving. This statement is true.
What about air, the atmosphere? Air does have mass. The particles are just very far
apart, so air feels light. The atmosphere is the layer of
gases or the air that surrounds the Earth. These gases are necessary for all
life. The atmosphere is made from gases
such as nitrogen gas, oxygen gas, carbon dioxide gas, water vapor, and small amounts
of other gases. If the Earth did not have gravity,
gas particles in the air would just float away into space. Organisms would not survive without
these gases and the atmosphere. But gravity pulls on the atmosphere
and holds it to the Earth. Since gravity does have an effect
on the atmosphere, we can see that statement (D), it has no effect on the
atmosphere, is incorrect.
We were asked to select the
statement which is not true. So statement (D), it has no effect
on the atmosphere, is the correct answer.
