Use the absolute and relative uncertainty to determine which is more precise mass or volume g

In respect to the question asked and the narrative in the explanation, volume g is more precise compared to mass.

Explanation:

First of all, we need to define what absolute uncertainty and relative uncertainty is.

Absolute Uncertainty: Absolute uncertainty is the number which when  combined with a reported value, gives the range of true values. For instance,  a length may be reported as 7.3 mm ± 0.2 mm. Here, the reported value is  7.2 mm and the absolute uncertainty is 0.2 mm; the range of true values is  7.1 mm to 7.5 mm. Absolute uncertainties always have the same units as the  reported value with which that are associated. When you are told to report  “the uncertainty” with your results, you should give the absolute uncertainty.

Relative Uncertainty: The relative uncertainty is the ratio of the absolute  uncertainty to the reported value. A length of 100 cm ± 1 cm has a relative  uncertainty of 1 cm/100 cm, or 1 part per hundred (= 1% or 1 pph). Relative  uncertainties do not have. Multiplying the relative uncertainty by the  reported value yields the absolute uncertainty. For instance, a mass of 2.042  g which has a relative uncertainty of 3 parts per thousand (3 ppt) should be  reported as 2.042 g ± 0.006 g.  

truck y has a greater velocity than truck x.

it is a negative acceleration