You can find electric power lines under the ground by looking for magnetic fields at ground level. this is best explained by which of these statements?
a) all wires have magnetic materials in them.
b) an electric current in a wire produces a magnetic field.
c) the power company puts magnets to find the power lines.
d) the iron in the ground is disturbed by the power lines creating magnetic fields

An athlete swings a ball, connected to the end of a chain, in a horizontal circle. the athlete is able to rotate the ball at the rate of 8.13 rev/s when the length of the chain is 0.600 m. when he increases the length to 0.900 m, he is able to rotate the ball only 6.04 rev/s. (a) which rate of rotation gives the greater speed for the ball? 6.04 rev/s 8.13 rev/s (b) what is the centripetal acceleration of the ball at 8.13 rev/s? m/s2 (c) what is the centripetal acceleration at 6.04 rev/s? m/s2