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  

a stronger central government  

its what they are

b

being given a fair trial before a jury