A4-kg block and a 2-kg block can move on the horizontal frictionless surface. the blocks are accelerated by a+12-n force that pushes the larger block against the smaller one. determine the force that the 2-kg block exerts on the 4-kg block.
a) -4 n
b) -12 n
c) 0 n
d) +4 n
e) +8 n

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.