Natural Sciences Grade 7 Term 4 Planet Earth

Natural Sciences Grade 7 Term 4: Planet Earth and Beyond Relationship of the Moon to the Earth

Topic 2 Relationship of the Moon to the Earth Gravity Natural Sciences - Grade 7

Centre of gravity • The centre of gravity can be described as the point in a body/system around which its mass/weight is evenly balanced/distributed and through which the force of gravity acts. • Mass [how much matter is in an object] is measured in kilograms. • An object’s mass stays the same, irrespective where it is [Moon/in space/ on Earth]. • Weight is measured in Newtons and it is the measurement of the pull gravity on an object. Natural Sciences - Grade 7

Centre of gravity • Look at the pictures and discuss each one: Natural Sciences - Grade 7

The force of gravity • The force of gravity causes the ball to return to the surface. • The weight force of gravity [Fg] causes the apple to drop to the ground. • Why are astronauts floating in space? Natural Sciences - Grade 7

Gravity role in the solar system • • • The gravitational pull of the Sun, keeps the Earth orbiting the Sun. The Earth’s and Sun’s gravity has an effect on the Moon’s motion. The Moon’s gravity causes the: - sea levels to rise and fall - ocean tides to rise and fall • Earth’s atmosphere is kept in place through gravity. • Gravity pulls on the clouds when the Earth spins on its own axis and it can have an effect on the weather. Natural Sciences - Grade 7