# Error analysis, multiplying an error

#### bingoboy

Equation: M (ΔT)=
The question:
If ΔT has an error of one degree, and i multiply it by the mass of an object (m) is the error in y still one

Attempted answer: or is it proportional to M i.e Δt plus or minus 1 degrees so the error in y is 2M?

P.S i need to be able to know the error for a whole bunch of values because im putting m delta t as an axis on a graph, would i have to work it out for each value of m ΔT

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#### harrylin

Hi welcome to physicsforums. I suppose that with "degree", you mean degree Celcius. If you multiply with a constant (thus the constant has no or negligible error) then the percentual error remains the same.

You can find that answer yourself simply by trying:

5x20=100
5x21=105

Last edited:

#### uby

generally speaking, if you have an error in x then the error in y will be the derivative of the function used on x times the error in x. for a straight line, the derivative is a constant value, thus the error in y is a constant value times the error in x.

#### bingoboy

yeah thanks harrylin thats exactly what i was trying to figure out, much appreciated