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

[单选题]
A student measures twa ma;fox-:q /1kj4 fqan;-djbfn s5(2o1gn1z a dvu8oo lengths 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 willvuv s 4tttab1ifemo1-ond8 -iy0b :3,y d1)wb result from the largest absolute uncertainty divided by the smallest measurement value. A and B havv,s 18mv3ydiu4) o01 :-ybie obtawd1ft tb- ne an 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.