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Earth, Space, and Gravity - Understanding Gravity and Airlessness

Grade 5CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Gravity is an invisible force of attraction that pulls all objects toward each other. On Earth, this force pulls everything toward the center of the planet, which is why objects fall down when dropped.

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Mass (mm) is the amount of matter in an object and remains constant everywhere in the universe. It is usually measured in kilograms (kgkg).

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Weight (WW) is the measure of the pull of gravity on an object. Unlike mass, weight changes depending on the gravitational pull of the planet or moon you are on.

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Air resistance (or drag) is a force acting opposite to the motion of an object through the air. On Earth, light objects like feathers fall slowly because of air resistance.

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Airlessness refers to a vacuum, such as outer space, where there is no air. In a vacuum, there is no air resistance, so a hammer and a feather dropped at the same time would hit the ground simultaneously.

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The gravitational pull of the Moon is much weaker than Earth's. Gravity on the Moon is approximately 16th\frac{1}{6}^{th} of the gravity on Earth.

📐Formulae

W=m×gW = m \times g

gEarth≈9.8 m/s2g_{Earth} \approx 9.8 \text{ m/s}^2

gMoon≈1.6 m/s2g_{Moon} \approx 1.6 \text{ m/s}^2

WMoon=WEarth6W_{Moon} = \frac{W_{Earth}}{6}

💡Examples

Problem 1:

An astronaut has a mass of 60 kg60\text{ kg} on Earth. What will be their mass on the Moon?

Solution:

60 kg60\text{ kg}

Explanation:

Mass is the amount of matter in an object and does not change regardless of location. Therefore, the mass remains 60 kg60\text{ kg} on both Earth and the Moon.

Problem 2:

If a school bag weighs 30 N30\text{ N} on Earth, calculate its approximate weight on the Moon.

Solution:

WMoon=30 N6=5 NW_{Moon} = \frac{30\text{ N}}{6} = 5\text{ N}

Explanation:

The gravity on the Moon is roughly 16\frac{1}{6} of Earth's gravity. To find the weight on the Moon, we divide the weight on Earth by 66.

Problem 3:

Why does a piece of paper fall more slowly than a stone on Earth, but they would fall at the same speed on the Moon?

Solution:

On Earth, the paper experiences significant air resistance due to its surface area. On the Moon, there is a vacuum (airlessness).

Explanation:

In the absence of air (a vacuum), there is no air resistance to push up against the falling objects. Therefore, gravity acts on both objects equally, making them fall at the same rate of acceleration: a=ga = g.