Question

activity b: planetary orbits
get the gizmo ready:

• click reset.
• click the “zoom in” button (⊕) several times to zoom in as far as possible.

introduction: johannes kepler (1571 - 1630) was a german astronomer who spent years poring over a vast store of planetary data compiled by his predecessor, tycho brahe. after many incorrect theories and other set - backs, kepler at last determined the beautifully simple physical laws that govern orbiting bodies. these rules are now known as keplers laws.
question: what rules describe the size and shape of planetary orbits?
observe: select mercury from the solar system menu. look at mercurys orbit.
a. what do you notice? ________
b. is mercury always the same distance from the sun? ________
keplers first law states that an orbit is in the shape of a slightly flattened circle, or ellipse. while a circle contains a single point at its center, an ellipse contains two critical points, called foci. the sun is located at one focus of a planets orbit.
gather data: the eccentricity of an ellipse describes how “flattened” it is. a circle has an eccentricity of 0, and a flat line segment has an eccentricity of 1.
a. look at the data displayed at left. what is the eccentricity of mercurys orbit? ________
b. zoom out to look at the other orbits. which objects orbit is even more eccentric than the orbit of mercury? ________
observe: zoom in all the way, and select mercury again. check that the simulation speed is slow and click play. observe the speed of mercury as it goes around the sun.
what do you notice? ________
keplers second law states that a planet speeds up as it gets closer to the sun, and slows down as it moves farther away.
confirm: change the speed to fast and zoom out to observe pluto. does pluto follow keplers second law? explain. ________

Explanation:

Step1: Identify orbit shape

Based on Kepler's first law, orbits are ellipses.

Step2: Determine distance variation

Since the orbit is an ellipse, the distance from the Sun varies.

Step3: Read eccentricity value

Read from the given data display.

Step4: Compare eccentricities

Based on simulation data for different objects.

Step5: Observe speed change

According to Kepler's second law.

Step6: Analyze Pluto's motion

Apply Kepler's second law to Pluto's orbit.

Answer:

A.

1. The orbit of Mercury is an ellipse.
2. No.
3. (Value needs to be read from the data displayed on - left in the actual simulation, not provided here).
4. (Answer depends on the data from the simulation, for example, Pluto has a highly eccentric orbit in the solar - system).
5. Mercury speeds up when it is closer to the Sun and slows down when it is farther away.
6. Yes, Pluto follows Kepler's second law. As Pluto moves closer to the Sun in its orbit, it speeds up, and as it moves farther away, it slows down, which is in accordance with Kepler's second law.