- #1

- 1

- 0

## Main Question or Discussion Point

Hi all,

Newbie here. Forgive if I'm starting this thread in the wrong place! Started college physics this semester and although the physics is not the most challenging, I'm running into lots of trouble with the sig figs! First of all, when doing long calculations, where do you round the sig figs? Just a quick problem: Plane in the wind, heading south at 185 km/hr, after an hour the place has only gone 135 km at 15 degrees East of South. I know how to do this, but I ran into trouble with the first part in finding the Southern displacement.

cos(15)*135 = southern displacement.

Does this equation equate to 2 significant figures because of cos(15)? Or is it 3 from 135?

Another example that I had trouble with is a question about finding where a long jumper will land. I found the initial velocity, used that to find how long the jumper was in the air with Vi, and solved for t with the quadratic equation. But, again, the sig figs are haunting me. Should I round them when I find the initial velocity and then use the rounded velocity in the quadratic equation? Or should I use the raw initial velocity in the quadratic equation, then round after? I am thoroughly confused with this, because then I don't know where in the quad formula to round!

If someone could clear this up I would REALLY appreciate this. I am normally an A+ student but my grades are suffering because of the sig fig confusion. Again, I thank you so much if you can help even guide me in the right direction.

(EDIT) I am not asking for any of my homework to be solved. I can complete it, just the sig figs part I don't know where to start!

Newbie here. Forgive if I'm starting this thread in the wrong place! Started college physics this semester and although the physics is not the most challenging, I'm running into lots of trouble with the sig figs! First of all, when doing long calculations, where do you round the sig figs? Just a quick problem: Plane in the wind, heading south at 185 km/hr, after an hour the place has only gone 135 km at 15 degrees East of South. I know how to do this, but I ran into trouble with the first part in finding the Southern displacement.

cos(15)*135 = southern displacement.

Does this equation equate to 2 significant figures because of cos(15)? Or is it 3 from 135?

Another example that I had trouble with is a question about finding where a long jumper will land. I found the initial velocity, used that to find how long the jumper was in the air with Vi, and solved for t with the quadratic equation. But, again, the sig figs are haunting me. Should I round them when I find the initial velocity and then use the rounded velocity in the quadratic equation? Or should I use the raw initial velocity in the quadratic equation, then round after? I am thoroughly confused with this, because then I don't know where in the quad formula to round!

If someone could clear this up I would REALLY appreciate this. I am normally an A+ student but my grades are suffering because of the sig fig confusion. Again, I thank you so much if you can help even guide me in the right direction.

(EDIT) I am not asking for any of my homework to be solved. I can complete it, just the sig figs part I don't know where to start!

Last edited: