Download física y química – 4.º eso – everest primer trimestre – evaluación

Phys. and Chem. 4th ESO. Overcoming Sky-Earth barrier. Astronomy and gravity Name:
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ANSWERS: Mark the correct option and give reasons for your choice. GOOD LUCK!
1.- a b c d REASONING AND EXPLANATION ________________________________________________________________
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2.- a b c d REASONING AND EXPLANATION _______________________________________________________________
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3.- a b c d REASONING AND EXPLANATION _______________________________________________________________
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4.- a b c d REASONING AND EXPLANATION _______________________________________________________________
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QUESTIONS (GOOD LUCK!):
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A satellite orbits the Earth at a constant speed and at constant height above the Earth’s surface.
a) No force is needed to keep it in its orbit.
b) As the satellite orbits, its velocity remains constant (remember that velocity is a vector quantity).
c) The forces on the satellite are balanced.
d) A force is needed to keep it in its orbit.
A geostationary satellite orbits the Earth along a path of radius 4.23 x 107 m. Its mass is 5 x 103 kg.
a) The satellite has a period of rotation, T=1 year.
b) The speed of the satellite around the Earth is 10,000 ms-1.
c) In this case, the centripetal force is the gravitational force and has a value of 1.12 x 103 N.
d) The gravitational acceleration at the height of the satellite is bigger than on the Earth surface.
When we observe the planets, we are looking at moving objects from another moving object, the Earth.
a) Looking to Mars, you notice that, night after night, its position changes in the background stars.
b) The planets movement didn’t have anything to do with heliocentric or geocentric ideas.
c) In ancient times, everybody (Aristoteles, Platon, Aristarco of Samos) agreed with geocentric theory.
d) Galileo didn’t have any problem due to his heliocentric ideas.
Choose the correct option:
a) The gravitational force between two stars of masses 4 x 1033 kg and 6 x 1030 kg, separated by 3.65 x
1020 m is 7 x 108 N (G = 6.67 x 10-11 UI).
b) The Sun will die in a spectacular gigantic explosion called supernova.
c) The Universe could end in a Big Crunch.
d) When the Sun, Moon and the Earth are lined up, the tidal range is lower than normal and the tides are
called neap tides.