We are told that the the individual is genotypically heterozygous, that is the have both types of the finger allele: the 5 finger allele and the 6 fingers allele however phenotypically, 6 fingers are observed. From this we can conclude that the 6 fingers allele is the one that is dominant because it is the one that is expressed phenotypically.
The larger mass object would have more kinetic energy. 1) its heavier 2) it covers a larger area 3) the more mass an object has, the larger the kinetic energy because of its weight.