f.4 phy, 拆力問題

Let T1 and T2 be the tensions in wire BA and BC respectively.

In fact, to resolve the forces, you just need to resolve the components to two perpendicular directions, in which they are independent of each other.

So, vertically, the vertical components of T1 and T2 balance the weight of the lamp.

T1sin60* + T2sin45* = mg

T1sin60* + T2sin45* = 40(10) = 400 ... (1)

Horizontally, the horizontal component of T1 balances that of T2.

T1cos60* = T2cos45* ... (2)


Solving equations (1) and (2):

T2 = 207 N

T1 = 293 N

Therefore, the tension in wire BA is 207 N while in wire BC is 293 N.