Why Is Answer A Correct for the Oscillation Problem?

[magiclink]

Homework Statement

Hi! My question is about oscillation. The multiple choice answers and question is included in the picture attached! I also happen to know the answer is A by looking at the marscheme.

The Attempt at a Solution

I would've thought that since the ball is said to be held "stationary" in that position the forces would all have to be equal. Thus i would've thought C was the correct answer. If they had said that it's an oscillation where the ball is in position P and not mentioned it being held stationary, I would've answered A, however, knowing that the forces would've had to be unbalanced and acting towards the equilbrium point. Could anybody explain exactly why it's A? and not C? I think my problem is probably largely due to interpretation of the question. Thankyou for any replies!

 

[gneill]

If the ball is stationary then the forces must sum to zero net force. If they were all equal, would the sum be zero? Remember, you're adding vectors here.

 

[Vipho]

Hi, magiclink!
Is that IB Physics?

 

[magiclink]

Hey! I just looked at the question and gave it a good look again. Turns out that the vectors did add vectorally to equal zero. A bit of an optical illusion to me. Thanks anyways! Sorry for wasting your time! :)


And yes, tis IB physics indeed. ;)