In the diagram above, MN is perpendicular to ON and MP. What is the difference between the moment about N of the force of 20 Newtons applied along MP and its moment about O?
Zero
0.2N.m
0.4N.m
0.8N.m
0.6N.m
Explanation
Video Explanation
No video available
Post your Contribution
Discussions (14)
Taking moment about point N:
P×distance MN
but we don't know dist. MN so we solve for it using Pythagoras theorem.
0.5²=0.3²+MN²
MN=0.4
.'. moment about N is
20×0.4=8Nm
The next thing is to take the moment about O ( use arrangement of lines of force into a triangle )
The moment displaced an angle so
Sinø=0.3÷0.5
Ø=36.87°
Moment about O = 0.5×20×cos(36.87)
O=8Nm
.'. difference between moment about O and N is 8-8=0
There is absolutely no need to go through any calculation for this question! Since Moment of force = Force × Perpendicular distance and looking at the diagram carefully, you will notice that point O and point N are at the same perpendicular distance to the 20N Force. So, it simply means they will have the same moment, so their difference will be zero!
Taking moment about point N:
P x distance MN
but we don't know the distance MN so we solve for it
using Pythagoras theorem.
0.5 ^ 2 = 0.3 ^ 2 + M * N ^ 2
MN = 0.4
.. moment about N is
20 * 0.4 = 8Nm
The next thing is to take the moment about O
Cos∅= 0.4/0.5
Moment about 0 = FDCos∅= 0.5 * 20 * 0.4/0.5
O = 8Nm
.. difference between moment about O and N
is 8-8=0
