Motion in the Universe: Answers
Define the terms: satellite, galaxy, asteroid and universe.
A satellite is anything in space which travels in an orbit. Satellites can be artificial or natural. Artificial satellites include the International Space Station whereas natural satellites are things like moons and comets.
Describe the shapes of the orbitals of planets, moons and comets.
Planets and moons travel in a (nearly) circular orbit. Comets travel in elliptical orbitals.
What is a comet?
Comets are lumps of ice which orbit the Sun. Heat from the Sun causes the ice to vaporise which looks like a ‘tail’ as the comet travels through space.
How does the speed of a comet change as it travels closer to other planets or the Sun?
The speed of a comet increases as it passes close to the Sun or to other planets due to gravitational pull.
What two factors influence the strength of a gravitational field?
The mass of the object and the distance from the object both affect the strength of the gravitational field. Larger objects will have a stronger gravitational field than smaller ones. The further the distance from an object, the weaker the gravitational field strength.
Calculate the orbital speed of Earth as it travels around the Sun. The radius of its orbital is 150,000,000 km and it takes 365 days for the Earth to travel around this orbit.
Orbital speed = (2 x pi x radius) / time period
Convert 365 days into seconds = 365 x 24 x 60 x 60 = 31,536,000
(2 x pi x 150,000,000) / 31,536,000 = 30 km/s