Kognity IB Physics A.0 Measurements & Uncertainty (id: 294aaa607)

[单选题]
The length of a pencx;)y y:pjuoi* il pgwf0sl8ou; qg /wltu8m7 +x.b h7w*i is measured using part of a measuring tape as shown below.t/ ;. 7w8u*l0lg mwgs +x7ufob8 qhipw

What is the length of the pencil?

A. $4.5 \pm 0.1 \; cm$
B. $11.5 \pm 0.2 \; cm$
C. $11.5 \pm 0.3 \; cm$
D. $11.5 \pm 0.5 \; cm$


参考答案:  D


本题详细解析:
We should be looking at the cm scale! The uncertainty in1h9ns 0dosnlg8z-d g* a reading on a scale is usually taken as half the smallest division. Here the smallest division is 0.5 cm so we can read each point on the scale to an accuracy of 0.25 cm. To find the length of the pencil we must take two no81gns0zh *ddl-gs9 measurements - one for each end of the pencil. This means that we must also add the uncertainties, giving an uncertainty of 0.5cm.