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

[单选题]
A student measures two 3xara 87xf b5alengths/s-ehp ulk/3 z;nm /pc as follows: $$a = (10 \pm 0.1) \; cm$$ $$b = (20 \pm 0.1) \; cm$$
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 fro;r/w 0l2 ii;iqzho*u dm the largest absolute uncertainty divided by the smallest measurement value. A and B have an absolute uncertainty of 0.1 cm, while for C & D it is 0.2 cm.i0dz;/ h l*iiru;q w2o So the percentage uncertainties are: A 1%; B 0.5%; C 0.67%; and D 2%. Clearly D is the largest.