Why doesn't a satellite in orbit fall down to Earth?

It is too far away for Earth's gravity to pull it down Its engines constantly push it upward to cancel gravity It moves so fast horizontally that as it falls, Earth's curved surface falls away at the same rate Zero gravity in space means nothing pulls the satellite toward Earth

What provides the centripetal force that keeps a satellite in a circular orbit?

The satellite's engine thrust Magnetic forces from Earth's core Gravity from Earth, directed toward Earth's centre The centrifugal force pushing the satellite outward

Johannes Kepler discovered that planetary orbits are not circles but ellipses. Where is the Sun located in a planetary ellipse?

At the exact centre of the ellipse At one of the two foci of the ellipse, not at the centre Outside the ellipse, because the Sun is too large to fit inside At the far end of the ellipse, furthest from Earth

Kepler's Second Law states that a line from the Sun to a planet sweeps equal areas in equal times. What does this imply about a planet's speed?

The planet moves at constant speed throughout its orbit The planet moves faster when further from the Sun The planet moves faster when closer to the Sun and slower when further away The planet's speed depends on its mass, not its distance from the Sun

A higher orbit (further from Earth) requires a satellite to move at a higher or lower speed to maintain orbit?

Higher speed — it has further to travel each orbit The same speed — orbital speed is constant regardless of altitude Lower speed — gravity is weaker further out, so less centripetal force (and speed) is needed Speed depends on the satellite's mass, not its altitude

What is 'free fall'?

Falling without air resistance — only applies to objects in a vacuum Motion under gravity alone, with no other forces acting — the object accelerates at g regardless of mass Falling faster than the speed of sound Any downward motion, including sliding down a slope

Earth orbits the Sun once every 365.25 days. Mars takes about 687 days. What does Kepler's Third Law tell us this implies about Mars's orbit?

Mars is smaller than Earth so it takes more time to complete each rotation Mars's orbit is larger — planets further from the Sun take longer to complete one orbit Mars moves faster than Earth, so it has a longer orbit period Mars takes longer because it has two moons slowing it down

What causes ocean tides on Earth?

The Moon's magnetic field pushes ocean water around Earth The rotation of Earth flings ocean water outward at the equator The Moon's gravitational pull is stronger on the near side of Earth than the far side, stretching the oceans into two bulges Solar wind from the Sun pushes water around the planet twice daily

What is a geostationary orbit, and why is it useful?

An orbit where the satellite never moves — held in place by two equal gravitational pulls An orbit at the right altitude where the satellite's orbital period equals 24 hours — so it appears stationary over one spot on Earth, ideal for communications The lowest possible orbit, where satellites can be easily reached for repairs Any orbit above the atmosphere where a satellite does not need engines

The Moon is gradually moving further from Earth at about 3.8 cm per year. What does Kepler's Third Law predict about Earth's future tides and lunar month?

Tides will become stronger and the lunar month will become shorter Tides will stay the same but the lunar month will shorten Tides will become weaker and the lunar month (time for Moon to orbit Earth) will become longer Nothing will change — tides and the lunar month are independent of the Moon's distance