In the video, the torque due to the mass of the plank is used in the calculations. For this question, ignore the mass of the board. Rank, from largest to smallest, the mass mm needed to keep the board from tipping over.

mass ranked largest to smallest.

D 200 kg, A 100 kg, B 100 kg, C 50 kg, E 33.33 kg.

Explanation:

Question is completed using google.

Use principle of moments about the point which will act as pivot when the plank tip over i.e. the edge of surface, to solve this question.

mass 1*moment arm 1=mass 2*moment arm 2

Figure A:

m*1.5=100*1.5

m=150/1.5=100 kg

figure b:

m*0.75=100*0.75

m=75/0.075=100 kg

figure c:

m*1.5=100*0.75

m=75/1.5=50  kg

figure d:

m*1.5=200*1.5

m=300/1.5=200 kg

figure e:

m*1.5=100*0.5

m=50/1.5=33.33 kg

the higher the current the higher the mag field around it the higher the influence on the compass

a is the best answer your welcome