In Federalist 78 Hamilton writes this about the judiciary: "It may truly be said to have neither FORCE nor WILL but merely judgment; and must ultimately depend on the aid of the executive arm even for the efficacy of its judgments."
a. What does this mean?

The Judiciary cannot physically enforce a law without the Executive and Legislative

Explanation:

Alexander Hamilton's essay Federalist 78 justifies the structure of Judiciary along with its shortcomings.  

Federalist No. 78 views the inability of judicial branch as an inherent weakness. It can neither control the money or military.

He says Judiciary has "no influence over either the sword or the purse". Judicial branch has the power of judgment which is driven by Executive and Legislative. It never functions independently without the aid of Executive. He says that Federal judiciary has the power to determine constitutional validity but cannot enforce it in isolation  

jim crow law, in u.s. history, any of the laws in which racial was enforced, in the south between the finish of reconstruction in 1877 and the start of the social liberties development during the 1950s.

jim crow was the name of a minstrel routine( jump jim crow) performed starting in 1828 by its creator, thomas dartmouth ("daddy") rice, and by numerous imitators, including on-screen character joseph jefferson.

the term came to be a defamatory sobriquet for african americans and an assignment for their segregated life. the segregation rule was stretched out to parks, graveyards, theaters, and eateries with an end goal to keep any contact among blacks and whites as equivalents.

it was classified on neighborhood and state levels and most broadly with the "separate yet equivalent" choice of the u.s. preeminent court in plessy v. ferguson (1896).