Always use significant figure rules. remember that these rules apply to all numbers that are measurements. compute the resistance of a 90-cm length of copper wire with a 0.020 -cm2 cross-sectional area. ( = 1.8 x 10-6 ohm-cm) r = ohms a 4.0 x 10^-1 b 1.3 x 10^11 c 8.1 x 10^-3 d 2.5 x 10^9

A14 kg rock starting from rest free falls through a distance of 5.0 m with no air resistance. find the momentum change of the rock caused by its fall and the resulting change in the magnitude of earths velocity. earth mass is 6.0 * 10^24 kg. show your work assuming the rock earth system is closed.