Which is the best description of Earth’s orbit?(1 point)

The best description of Earth's orbit is **almost circular**. While Earth's orbit is technically an ellipse, it is very close to being circular, with a low eccentricity.

Which orbital shape did most scientists in the early 1600s think the planets of our solar system have?(1 point)

Responses

hyperbolic
hyperbolic

elliptical
elliptical

parabolic
parabolic

circular

Most scientists in the early 1600s thought the planets of our solar system had a **circular** orbital shape. This belief persisted until Johannes Kepler proposed his laws of planetary motion, which demonstrated that planetary orbits are elliptical.

Which planet’s orbit was Kepler first studying when he began to develop his laws of orbital motion?(1 point)

Responses

Saturn
Saturn

Jupiter
Jupiter

Earth
Earth

Mars

Kepler was first studying the orbit of **Mars** when he began to develop his laws of orbital motion. His observations of Mars' trajectory led to the formulation of his first two laws.

Which of these describes Kepler’s third law of orbital motion?(1 point)

Responses

T3 ∝a2
T3 ∝a2

T2∝a
T2∝a

T2 ∝ a3
T2 ∝ a3

T∝a2

Kepler's third law of orbital motion is described by **T² ∝ a³**, where T is the orbital period of a planet and a is the semi-major axis of its orbit. This law states that the square of the period of a planet's orbit is directly proportional to the cube of the semi-major axis of its orbit.

Which statement describes Kepler’s third law of orbital motion?(1 point)

Responses

The square of orbital period is proportional to the cube of the semi-major axis.
The square of orbital period is proportional to the cube of the semi-major axis.

The square of orbital period is proportional to the semi-major axis.
The square of orbital period is proportional to the semi-major axis.

The cube of orbital period is proportional to the square of the semi-major axis.
The cube of orbital period is proportional to the square of the semi-major axis.

The orbital period is proportional to the square of the semi-major axis.

The correct statement that describes Kepler’s third law of orbital motion is:

**The square of orbital period is proportional to the cube of the semi-major axis.**

This expresses the relationship \( T^2 \propto a^3 \), where \( T \) is the orbital period and \( a \) is the semi-major axis.