# How to Graph - help ASAP (1 Viewer)

#### el_manu

##### Member
I have a physics practical task really soon, and we are going to have to draw a graph.

Alright. A few questions.
1) Does your axis have to start at zero, or can you start it on whatever number you want?
2) How do you draw a line of best fit.
3) Where do you stop the line of best fit, do you make it hit the axis?
4) How do you calculate the gradient from the graph, do you use your line of best fit? And does it matter where on your line of best fit you take the gradient from?

#### InteGrand

##### Well-Known Member
I have a physics practical task really soon, and we are going to have to draw a graph.

Alright. A few questions.
1) Does your axis have to start at zero, or can you start it on whatever number you want?
2) How do you draw a line of best fit.
3) Where do you stop the line of best fit, do you make it hit the axis?
4) How do you calculate the gradient from the graph, do you use your line of best fit? And does it matter where on your line of best fit you take the gradient from?
1) You can start at non-zero numbers (or so our teachers said)
2) http://community.boredofstudies.org/18/physics/335522/line-best-fit.html
3) http://community.boredofstudies.org/18/physics/335522/line-best-fit.html (generally stop it so that it just goes through the range of x-axis values of your data points used for the LOBF, unless they tell you to otherwise (e.g. they may say to continue it down to the origin, but if they don't, you shouldn't do this in general))
4) Yes, you use your LOBF to calculate a gradient (and remember that the gradient will have units of: (units of y-axis quantity)/(units of x-axis quantity). And it does matter where on your LOBF you take the gradient from. You should try and take it from two points which are quite far apart on your LOBF, so that a small error in reading the coordinates of a point will not make a big difference. Also it is convenient for you if you can pick two points which happen to pass through a grid point on your grid paper, so you can more easily see the coordinates of point. And you probably know this, but the gradient formula is $\text{gradient} = \frac{y_2 - y_1}{x_2 - x_1}$, and you should write this formula in exam Q's and then substitute chosen points into it in your next line.

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thx heaps