Wednesday, July 31, 2013

IGCSE MATHEMATICS Topic : Plotting Lines From Exponential Equations

Given a straight line plotted on a graph we can estimate the values of the gradient and either using a point on the line or by estimating the y – intercept, we can find the equation of the line in the form The most convenient form in which to analyse the relationship between two variables x and y is the linear form, and we must see if, given a suspected relationship between two variables, we can construct a linear graph from the suspected relationship.
Suppose we suspect an exponential relationship between two variables. We also have the following data.
Time, t in s
10
20
30
40
50
Mass m in g
40.3
27
18
12.2
8.1
Our relationship will take the formTo transform this into a straight line we take logs of both sides obtaining,We recalculate the table.
Time, t in s
10
20
30
40
50
log (m)
3.696
3.296
2.890
2.501
2.092
And sketch the graph:
Comparingwithwe seeso andsothen

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