# Mini-Quiz: Length of Year for Planets in Gravitational Orbit

by Ron Kurtus

Take this Mini-Quiz to check your understanding of the lesson material.

1. If many orbits are elliptical, why is the circular orbit equation used?

The velocity for an ellipse is 2/3 the velocity of a circle

Values are easier to calculate and are close enough for most purposes

No one is really sure why scientists continue to use the circular equation

2. Why is the orbital period converted into Earth years?

It is because orbits are not true circles

It depends on what planet you are talking about

It is a convenient way to relate to the time it takes to orbit

3. What would the Earth's orbital period be if it was 4 times as far from the Sun than it is now?

The orbital period would be the same

The orbital period would be 8 years (2*2*2)

The orbital period would be 64 years (4*4*4)

If you got all three correct, you are on your way to becoming a Champion in Physics. If you had problems, you had better look over the material again.

Think positively

## Resources and references

Ron Kurtus' Credentials

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Acceleration due to Gravity Calculations - from Western Washington University

Gravitation Resources

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www.school-for-champions.com/science/
mini-quiz_gravitation_orbits_planetary_year.htm

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