Question

A force is represented in magnitude and
direction by the line joining the point A(1,-2,4) to the point B (5,2,3). Find its moment about the point (-2,3,5)

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Answer 1

Answer:

just use formula

F×R to get torque about given point

Answer 2

F=3i+k point about which moment is to be taken is i+2j−k.

∴x=  

OP

=P.V. of P−P.V of O =(2j−j+3x)−(i+2j−k) or r=i=3j+4k.

Hence the moment is r×F=(i−3j+4k)×(3i+k)

=  

∣

∣

∣

∣

∣

∣

∣

∣

​  

 

i

1

3

​  

 

j

−3

0

​  

 

k

4

1

​  

 

∣

∣

∣

∣

∣

∣

∣

∣

​  

=−3i+11j+9k.