Question

Global positioning satellites(GPS) can be used to determine positions with great accuracy.

Part A

If one of the satellites is at a distance of 20,000 km from you, what percent uncertainty in the distance does a 5m uncertainty represent?

Express your answer using one significant figure

Part B

How many significant figures are needed in the distance?

Express your answer using one significant figure.

If you could explain how you got the answer that would be great!

Answer 1

satellites distance from you r = 20,000 km

                                              = 20000 x 10 ³ m

uncertainty dr = 5 m

Percent of uncertainty = ( dr / r ) x100

                                     = 2.5 x 10 ^-5 %

(B). r = 20000 km

        = 20000000 m

8 significant figures are needed in the distance