10/17/2017 Tuesday
Science Log Semester 1 Week 8 Tuesday Oct 17 If a scaling factor is 1 cm: .001 m, is the actual object very big or very small? UPDATE MOON LOG
Earth/Moon model We have a model of Earth, but we don’t have a model Moon. What is a model? It’s an accurate representation of an object or system. It can be larger than reality, like a model of an atom or a cell. Or it can be smaller, like our model Earth. You are going to make a scaled model of the Moon to go with the model of Earth. Then positon your model Moon at the proper distance from model Earth to represent the distance from Earth to the Moon. With a scaled model of the Earth/Moon you will have a better sense of the size and distance relationships between them. First we need to find the scaling factor, which is the ratio of the real size to the model size. (add to page 60)
8. Measure Earth-globe diameter Measure the circumference or diameter of the globe How are we going to measure the diameter of the globe? Here are 3 possibilities: Pile up books until the globe will just fit under a ruler extending out from the top of the stack. Remove one of the plastic plugs from the globe, and use a straw like a dipstick to measure the diameter accurately. Measure the circumference with a meter tape or by rolling the globe across a surface. Divide that by pi (d=c/pi)
12. Finished models Look at the different models. Are the Earth models all the same size? Yes Are the Moon models all about he same size? Are the Moon models all located at about the same distance from the Earth models?
Earth/Moon Calculations (scale factor)
9. activity The globe is about 12 cm in diameter. Earth is 12,756 km or( about 12,750 km) in diameter. Each centimeter on the globe equals 1063 km (about 1,000 km) on Earth. (That makes the globe roughly 1/10,000,000 the size of Earth. ) The Moon is 3474 km (about 3500 km) in diameter (a little more than one-fourth the diameter of Earth). The model Moon should be about 3.3 cm in diameter (about the size of a table-tennis ball) to be properly scaled to the Earth globe. The Moon is about 384,000 km from Earth, so the model Moon should be about 361 cm (3.6 m) from the globe.
13. Answer the focus question page 66 What does a scaled Earth/Moon model look like? Compare your predictions with what we came up with.
14. New strategy There is a shortcut for making an Earth/Moon model We know how far away the Moon is in one unit –kilometers (384,000 km). We can also express the distance from Earth to the Moon in other units. Were going to use the diameter of the Earth as our standard unit (instead of km or cm)
14. New strategy What is the distance from Earth to the Moon in Earth diameters? Calculate the distance from Earth to the Moon in Earth diameters by dividing the distance to the Moon by the diameter of Earth. 384,000/12,756 = The Moon is about 30 Earth diameters away. Can you figure out the diameter of Earth in Moon diameters (by dividing the diameter of Earth by the diameter of the Moon) It is about 3.6 times the diameter of the Moon or, about 4 times the diameter of the Moon. It follows that the Moon is very roughly ¼ the diameter of Earth
Notes on study page 57 By using these relationships, any number of Earth/Moon models can be constructed by identifying The Moon is about ¼ the diameter of Earth and The Moon is at a distance of about 30 times the diameter of the Earth sphere. (or 30 Earth diameters from Earth)