Answer:
18.6012339739 A
Explanation:
= Vacuum permeability = 
L = Length of wire = 55 cm
N = Number of turns = 4000
I = Current
Magnetic field is given by

The current necessary to produce this field is 18.6012339739 A
That's called the "normal" to the surface at that point.
Answer:
6s
Explanation:
Assume it is dropped from rest and the gravitational acceleration is 10
By the equation of motion under constant acceleration:

180 = (0)t+10(t^2)/2
t = 6 or -6 (rejected)
t = 6 s
Answer:
The two methods will yield different results as one is subject to experimental errors that us the Archimedes method of measurement, the the density measurement method will be more accurate
Explanation:
This is because the density method using the calculated volume will huve room for less errors that's occur in practical method i.e Archimedes method due to human error