請教 2007 Physics MCQ14, 43,help

07-14.
sin50deg = n2 sinr
n2 = sin50deg/sinr
sin r = n2 sin 35deg
sin r = sin50deg sin 35 deg/sinr
sin^2 r = sin 50 deg sin 35deg
r = 41.5 deg (corr to 3 sig fig)
07-43.
Smaller, because at that time, an attractive force by magnet is acting on the copper. The force will partially decrease the weight of the copper.
Answer: C


2010-04-15 21:47:53 補充：
07-43,
Sorry I see the magnet gogin upwards = =
Actually, since the magnet going downwards,
Since there should be a repulsive force for repelling the copper downwards.
A force is added to the weight, therefore the copper is heavier and the reading goes greater.

圖片參考：http://j.imagehost.org/0884/ScreenHunter_08_Apr_15_21_42.gif


http://j.imagehost.org/0884/ScreenHunter_08_Apr_15_21_42.gif

thx for helping but Q43 should be answer D

2010-04-16 15:11:02 補充：
both are helpful