# Vectors: Magnitude of forces acing on stable object: A = 800kN, B = 650kN, so C = ?

#### NAC54321

##### New member

Having great difficulty in the following problem:

Magnitude of the 3 forces acing on a stable object

A = 800kN
B = 650kN
C = ?

What is the magnitude of force C?

Any feedback would b much appreciated.
Many thanks.

#### Subhotosh Khan

##### Super Moderator
Staff member

Having great difficulty in the following problem:

Magnitude of the 3 forces acing on a stable object

A = 800kN
B = 650kN
C = ?

What is the magnitude of force C?

Any feedback would b much appreciated.
Many thanks.
Forces are vectors. Those need to have three characteristic properties, when applied to a body. Those are:

Magnitude

Direction and

point of application.

You have given us only one of those (magnitude for A and B).

You need to define the other two in the problem statement before this problem can be solved.

#### NAC54321

##### New member
Hi Khan,

Thanks for the reply.
Unfortunately the question has very limited numbers, no angles etc.
The object is stable what is the magnitude of force C?

Many thanks. #### stapel

##### Super Moderator
Staff member
Unfortunately the question has very limited numbers, no angles etc.
The object is stable what is the magnitude of force C? The "below" is not displaying for the rest of us. Also, without any further information (than just the magnitude of two of the forces), there is no way to answer this question. Sorry! #### NAC54321

##### New member
Hi all,

I have tried to attach a basic sketch of the question.
Apart from west, south directions,
Magnitude A(west) = 800 kN
Magnitude B (south)= 650 kN
Magnitude C (figure shows approximate direction it says) = ?

Thankyou

#### Attachments

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#### Subhotosh Khan

##### Super Moderator
Staff member
Hi all,

I have tried to attach a basic sketch of the question.
Apart from west, south directions,
Magnitude A(west) = 800 kN
Magnitude B (south)= 650 kN
Magnitude C (figure shows approximate direction it says) = ?

Thank you
That sketch makes the problem solvable!

Have you been taught about Cartesian unit vectors?

#### stapel

##### Super Moderator
Staff member
Apart from west, south directions,....
Yes; directions; that's exactly what we'd been asking for! Your unfamiliarity with how vectors work suggests that you might not be entirely familiar with what they are, or with how to solve this sort of exercise...? Do you need lesson links, so you can study up on this topic?

Thank you! #### NAC54321

##### New member
Thanks for both replies, much appreciated.
I've done basic vectors in lectures but nothing like the above.
I clearly need to study up on this, any clear direction to study which would help me answer this question would be good.

Are you both saying that this problem is more than just a magnitude formulae?

What are the clear steps to solve this problem? Also determine angles etc? I understand that there is a 90 degree difference between A &B, just struggling with what the other steps that are required?

Again, thanks for your continued help.