Suppose a spacecraft orbits the moon in a very low, circular orbit, just a few hundred meters above the lunar surface. the moon has a diameter of 3500 km, and the free-fall acceleration at the surface is 1.6m/s2. how fast is this spacecraft moving?
a. 53 m/s
b. 75 m/s
c. 1700 m/s
d. 2400 m/s

Currents in dc transmission lines can be 100 a or higher. some people are concerned that the electromagnetic fields from such lines near their homes could pose health dangers. for a line that has current 150 a and a height of 8.0 m above the ground, what magnetic field does the line produce at ground level? express your answer in teslas and as a percentage of the earth’s magnetic field, which is 0.50 g. is this value cause for worry?