A 2kg ball is rolled along the floor for 0.8 m at a constant speed of 6 m/s. What is the work done by gravity? A, 0
B, 16 J
C, 72 J
D, 450 J
E, 90 J

Along wire carrying a 4.2 a current perpendicular to the xy-plane intersects the x-axis at x=−1.7cm. a second, parallel wire carrying a 3.0 a current intersects the x-axis at x=+1.7cm. part a at what point on the x-axis is the magnetic field zero if the two currents are in the same direction? express your answer to two significant figures and include the appropriate units.