Mechanical Engineering - Engineering Mechanics - Discussion

Discussion Forum : Engineering Mechanics - Section 1 (Q.No. 49)
49.
two like parallel forces are acting at a distance of 24 mm apart and their resultant is 20 N. It the line of action of the resultant is 6 mm from any given force, the two forces are
15 N and 5 N
20 N and 5 N
15 N and 15 N
none of these
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
24 comments Page 1 of 3.

M. Flowers said:   1 decade ago
I'm not understanding what method you applied to get these answers. What formula was used?

Pradeep said:   1 decade ago
Nothing the method is used here, It is simple, If a number of forces are applied on a body, then all the forces are replaced by a resultant force (algebraic sum of all forces). Here, there is no mean of distances given.

Dr.. Ramesh B. R said:   1 decade ago
f1+f2 = 20 --->1.

Moment of the resultant about a point shall be equal to moment of the forces about the same point. Therefore take moment of the forces on a point abve resultant.

R*0 = F1*14-F2*6 ------>2.

Solving above two eqn.

F2 = 15N F1 = 5 N.

Rahul kumar said:   1 decade ago
Rahul kumar.

F1+F2=20-------> (1).
14F1-6F2=20-----> (2).

Solving equation (1)& (2).

F1 = 5N.
F2 = 15N.

DARSHAN said:   1 decade ago
F1+F2=20......(1).

NOW,
MOMENT about Resultant
18F1-6F2=0.....(2).

By solving above eq.
We get F1=5 & F2=15.

Rishi said:   1 decade ago
Where did 18f1 and 6f2 came from? I think you can simply add the forces as they are like and parallel. F1+F2=20 and option 1 satisfies it.

Fathima said:   10 years ago
Can you give us a schematic sketch?

Nithyananda said:   10 years ago
They are given F1=24, but I don't know why the two person taken as F1=14?

ROJ said:   10 years ago
F1+F2 = 20.......1

Here 24 mm means total distance.

Take moment about resultant.

Note that moment = force*moment arm.

R*0 = F1*(24-6)-F2(6).
0 = 18F1-6F2.

18F1 = 6F2.
F1/F2 = 6/18 = 1:3.

So F1 = 5 & F2 = 15.
(1)

Pandees waran said:   9 years ago
F1 + F2 = 20.

15 + 5 = 20 simple method.


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