Please help me with these three questions. I am very lost, and i\'d really appre

Question

Please help me with these three questions. I am very lost, and i'd really appreciate help. Thanks!
1. If we were to travel on a space ship at a speed of 9,000 km/hour, how many years would it takes us to reach Sirius, the brightest star in the sky?

2. The Earth rotates around its axis, covering its circumference in 24 hours. The radius of Earth on the equator is 6,370 km. Calculate the speed at which a point on the Equator rotates.

3. If we had the technology to travel at the speed of light, how long would it take us to do a trip around the world, i.e., to cover the whole Earth cir;cumference?

Explanation / Answer

1. sirius is 8.6 ly away
1 ly = 1013 km

8.6 ly = 8.6x1013 km

8.6x1013 km / 9000km/hr = 9.55 x 109 hrs

1 year = 24 * 356 = 8.54x103 hrs

9.55 x 109 hrs / 8.54x103 hrs = 1.12 x 106 years

2. the circumference at the equator is 2r, or 6370 * * 2 = 4x104 km

4x104 km/ 24 hrs = 1.667 x103 km/hr

3. speed of light = 3 x 105 km/s

circumference of the earth is 4x104 km

4x104 km / 3 x 105 km/s = .1333 seconds

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