Question

When mars is on the opposite side of the sun from earth, it is about 4.0×108km away. how long does it take a radio signal traveling at the speed of light, c=3.00×105km/s, to go from earth to mars at this time? be sure to give your answer with the appropriate precision?

Answer 1

1.2x10^4 s To determine how long the radio signal takes to travel the distance, just divide the distance by the speed of light. So 4.0x10^8 km / 3.00x10^5 km/s = Multiply the mantissa, so 4.0 * 3.00 = 12.000 Subtract the exponents 8 - 5 = 3 So the result is 12.000 x 10^3. But since 12 is greater than or equal to 10, we need to divide by 10 and add 1 to the exponent, getting 1.2000 x 10^4 s And since the least precise value we have has only 2 significant figures, we need to round the result to 2 significant figures, getting 1.2x10^4 As for the units, we had km divided by km/s so km / km/s = km * s/km = (km s)/km = s/1 = s Therefore the final result is: 1.2x10^4 s