Why we have to tap the frame during Deflection of Beam Experiment?

socrates_1

hi, last week we did an experiment to find the deflection of simply supported beams.
During the experiment, after every measurement we had to tap the frame slightly. Does anyone know why we had to do this?
If you could explain it to me I would be grateful.

Studiot

Welcome to Physice Forums

Firstly some protocol. You have posted duplicate threads. This is frowned upon, to put it mildly.

As to your question, did you not ask the lecturer at the time?.

If I were she I would have suggested you consider what force or forces might be acting that are not included in the general beam formulae you were testing.

socrates_1

Thank you for your response.
I cant find out what forces u mean. Could you explain it further?

AlephZero

Since you were measuring deflections, something probably moved between each measurement. What sort of force tends to prevent things from moving, in any real-world situation?

socrates_1

Friction?

Vadar2012

To set up the experiment you would of got some sort of beam and Clamped one end or both. The key word in there starts with a C.

socrates_1

Could someone else explain??I cant find out

Vadar2012

I just gave you the answer without actually telling you. Straight just telling you the answer is frowned upon here.

socrates_1

anyone who could actually tell me???

Studiot

Many engineers call it "stiction". It is the same reason that we tap any mechanical indicating device that relies on mechanical movement to indicate a value, such as a meter movement a dial gauge, a barometer etc.

http://en.wikipedia.org/wiki/Stiction

socrates_1

really thank you