A long plank XY lies on the ground. A load of 120N is placed on it, at a distance of 0.50 m from end X as shown. End Y is lifted off the ground. The upward force to do this is 65N.

In the diagram, W is the weight of the plank, acting at its mid-point.
What is the value of W?
A 35N
B 47N
C 100N
D 133N

Beryl states that insulation with the smallest possible thermal conductivity is best to keep a house warm in winter, but worst for keeping a house cool in summer. sapphire insists the reverse is true: low thermal conductivity is good in the summer, but bad in the winter. which one, if either is correct? a. beryl, because low thermal conductivity results in low heat transfer. b. beryl, because low thermal conductivity results in high heat transfer. d. sapphire, because low thermal conductivity results in high heat transfer. e. neither, because low heat transfer is desirable both in summer and in winter.