A planet X around a star S

The diagram shows an approximate orbit of a planet X around a star S.


Which of the following statements is false?

(a) The planet moves in an ellipse with the star at one focus.
(b) The planet moves at the same speed at points A and C.
(c) The planet moves fastest at point D.
(d) The potential energy of the planet changes during the orbit.


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Why is the Earth Round?

EarthNasaThe Earth, the Moon, the Sun, the stars and the planets round or spherical, because they have a very large mass. Their own gravitational force aims to give them the shape of a sphere.

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When does the Sky become Space?

ShuttleIf we are flying higher and higher it is meant to fly with greater and greater speeds. A speed, above a certain altitude, could be bigger than the circular orbital speed at that altitude.
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Will there be a time when new stars will not form?


Image Credit: ‪‎NASA‬, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team

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Can we move faster at night?

The more correct question is do we move faster at night?
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Can a candle burn in a spaceship?



Can a candle burn in a spaceship (in microgravity)?


Image Credit: NASA.
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The Polar Ice Cap Is Now Melting

imageAccording to NASA, the polar ice cap is now melting at the alarming rate and sea-level rise all around the Earth. This redistribution of mass will cause the Earth’s day to become

a) longer
b) shorter
c) stay the same
d) the earth will stop rotating
e) not enough information

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