Couple of uncertainty questions

[nugget]

1. The area of a circle has a fractional uncertainty of 0.08 (i.e. 8%), what is the fractional uncertainty of it's radius?

So i suppose you have to use A = pi(r^2) and rearrange, bit confused though...

2. Square wave has a height of 2.4cm +/- 0.2cm. This signal is applied across a resistor of R = 10.0 +/- 0.2 ohm. What is the fractional uncertainty in the heating power dissipated by the resistor?

Figured this is the right formula... P = (V^2)/R

again a bit unsure how to do it.

thanks

 

[berkeman]

1. The area of a circle has a fractional uncertainty of 0.08 (i.e. 8%), what is the fractional uncertainty of it's radius?

So i suppose you have to use A = pi(r^2) and rearrange, bit confused though...

2. Square wave has a height of 2.4cm +/- 0.2cm. This signal is applied across a resistor of R = 10.0 +/- 0.2 ohm. What is the fractional uncertainty in the heating power dissipated by the resistor?

Figured this is the right formula... P = (V^2)/R

again a bit unsure how to do it.

thanks

As you should know, we don't do your work for you. How should you use uncertainties and those formulas to calculate the final uncertainties? If the equation is linear, the transfer of the uncertainty depends on what? If the equation is non-linear, the uncertainty depends on what? Read your textbook...