Kepler’s Laws



|Earth Science |Name: |

|Kepler’s Laws Lab |Date: |

| |Block: |

Objective

After completing these three activities, you will better understand Kepler’s Laws and the impacts they have on planetary motion.

Activity 1: Mercury’s Orbit (Kepler’s First Law)

In this activity, you will be plotting the orbit of Mercury around the sun using data taken from 18 different position along Mercury’s orbit.

|Observation # |Degrees |Distance from Sun (AU) |Distance on graph paper |

|1 |4 |.35 | |

|2 |31 |.32 | |

|3 |61 |.31 | |

|4 |92 |.31 | |

|5 |122 |.32 | |

|6 |149 |.35 | |

|7 |172 |.38 | |

|8 |192 |.41 | |

|9 |209 |.43 | |

|10 |224 |.45 | |

|11 |239 |.46 | |

|12 |252 |.47 | |

|13 |266 |.47 | |

|14 |280 |.46 | |

|15 |295 |.44 | |

|16 |311 |.42 | |

|17 |330 |.40 | |

|18 |350 |.37 | |

1. Put a dot in the center of a piece of graph paper. This represents the Sun.

2. Use a protractor to put a dot at each of Mercury’s 18 positions (see the degrees column). Then, use a scale of 1cm=0.05AU to measure the distance from the Sun.

3. When you have plotted all 18 data points, connect the dots as smoothly as you can. You have now plotted the orbit of the planet Mercury.

Follow Up Questions:

1. Is the distance from the Sun to Mercury constant? ________________________

2. What shape is the orbit?______________________________________________

3. Is the orbit of Mercury highly elliptical or only a little elliptical? ______________

4. What is Kepler’s first law?

5. How does this activity relate to Kepler’s first law?

Activity 2: Mercury’s Orbit (Kepler’s Second Law)

In this activity, you will see if the area of a sector swept out from the Sun to Mercury remains constant between any two data points separated by EQUAL periods of time (as per Kepler’s Second Law)

1. Choose data points 2 and 3 as one pair, and data points 10 and 11 as another pair. Draw the radius out from the Sun to each data point. Call the sector formed by the lines to points 2 and 3 "sector A", and the sector formed by the lines to points 10 and 11 "sector B".

2. Lightly shade in the two sectors (you will need to easily see the grid lines). Count the number of complete squares in sector A and the number of complete squares in sector B. For any squares that lie along a line, estimate complete squares.

Eg.

These two combined would make about one complete square.

Follow Up Questions:

1. Compare the areas of sectors A and B. Are they approximately equal, considering the approximations we have made?

2. When do you think Mercury is moving faster, from data point 2 to 3, or data point 10 to 11? Why?

3. How does this activity relate to Kepler’s second law?

Activity 3: Orbital Period & Distance (Kepler’s Third Law)

In this activity, you will determine the relationship between orbital period (the time is takes for an object to move in a complete circle) and distance.

1. Cut three different lengths of string. Tie a rubber stopper securely around one end of the string.

2. Measure the length of the string once it has been fastened to the rubber stopper. Record your measurements in the table below.

3. Start swinging the rubber stopper around your head in a horizonal circle so it barely keeps tension on the string.

4. Have your partner start a timer and at the same time start counting the revolutions of the rubber stopper.

5. After 10 revolutions, stop the timer and record your results in the table below. Calculate orbital period using the equation given below.

Orbital Period = Time ÷ Number of Revolutions

6. Repeat with the other two pieces of string

7. Record all your results in a table in the space provided below.

| |Length |Time |Period |

|Trial 1 | | | |

| | | | |

|Trial 2 | | | |

| | | | |

|Trial 3 | | | |

| | | | |

8. What is the relationship between orbital period and distance (length)?

9. What is Kepler’s third law?

10. How does this activity relate to Kepler’s third law?

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