Kognity IB Physics A.0 Measurements & Uncertainty (id: 3dae35a97)

[单选题]
A student measures two len,3ll2ekc1b pvf /b ip6gths as follows: j h)v- vf/ c d3e2 iyt,:lc;ugi-w6azh$$a = (10 \pm 0.1) \; cm$$ $$b = (20 \pm 0.1) \; cm$$
Which of the following quantities has the largest percentage uncertainty?

A. $a$
B. $b$
C. $a+b$
D. $a-b$


参考答案:  D


本题详细解析:
The largest percentage uncertainty will result from the largest absolute uncertep j 9l y r;s91g:kg0-i,c.6 yg)fxjktmxn,r sainty divided by the smallest measurement value. A and B have an yr j-x 1g,,g) sxi 6kc0n9m: klpt9yrs;jfge.absolute uncertainty of 0.1 cm, while for C & D it is 0.2 cm. So the percentage uncertainties are: A 1%; B 0.5%; C 0.67%; and D 2%. Clearly D is the largest.