|Aug30-07, 03:50 PM||#1|
Lightyears and the surface area of a planet.
A light year is the unit of distance that light, with a speed of 2.99792e8 m/s, travels in one year. What is the surface area of a planet whose radius is 1300 km? Answer in units of lightyears^2.
I am wondering if my method is correct.
SA of a sphere is 4[pi]R^2. With R = 1300, the surface area is 6.76e6[pi] km^2. Since they want this number in terms of light years, I need to first, well, convert the ratio into years. With dimension analysis (not the internet), I found that there was 31536000 seconds in one year. Setting up a proportion, that's about 9.45e15 meters in one year, or 9.45e12 km in one year. I squared that number (this is the part I am most unsure about) and then divided 6.76e6[pi] by about 8.94e25 km^2, to get 2.38e-19. But I don't think that's right, because the dimensions actually cancel, then.
|Aug30-07, 04:05 PM||#2|
Blog Entries: 9
You should divide 6.76e6[pi] km^2 by 8.94e25 km^2/lighyears^2. The units will be okay.
|Aug30-07, 04:51 PM||#3|
I forgot about km^2 being overlightyears^2.
|Similar Threads for: Lightyears and the surface area of a planet.|
|Surface Area and surface Integrals||Calculus & Beyond Homework||4|
|Surface Area and Surface Integrals||Calculus & Beyond Homework||2|
|Surface w/ max volume and min surface area||Calculus||13|
|Surface Area (Surface of Revolution) - Discrepancy||Calculus||23|
|surface area and total area||General Math||12|