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

[单选题]
A student measures two lengths asndgipv0: t :6xr,*np *bhxaj9/hr+i b followpl) m-lgq ,xl)s: $$a = (10 \pm 0.1) \; cm$$ $$b = (20 \pm 0.1) \; cm$$
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 absolunlz;ed1o2(u -a14 rse frmo:g te uncertainty divided by the smallest measurement value. A and B have an absolut2le rurng ;d11ao:mf4- (eszoe 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.