Final answer:
The length of segment PQ' after dilation by a scale factor of 2 is 16 cm, calculated by doubling the original length of 8 cm.
Step-by-step explanation:
If the segment PQ is 8 cm in length and is dilated by a scale factor of r = 2, the new length of segment PQ' is calculated by multiplying the original length of PQ by the scale factor. This means we take 8 cm and multiply it by 2.
PQ' = |PQ| × r = 8 cm × 2 = 16 cm
Thus, the length of segment PQ' after the dilation is 16 cm.