Depends on what the area is. If it’s a rural place, Wood is cheep & easy to build. If there’s a lot of corrosion, strong weather/hurricane, bricks.
The weight of the person is given by:
W = mg
W = weight, m = mass, g = gravitational acceleration
Given values:
m = 40kg, g = 9.81m/s²
Plug in and solve for W:
W = 40(9.81)
W = 390N
Question 1
To find centripetal acceleration, use the formula : centripetal acceleration = v^2/r
so answer would be (3.71)^2/42.85=0.32 (2d.p.)
Question 2
Force =ma
a= (9.98)^2/31.77=3.1350
Force= 3.1350 * 56.63 = 177.54 (2 d.p.)
Answer:
The center of mass of the Earth–Moon system is 4.613 × 10⁶ m from center of the Earth.
Explanation:
Let the reference point be the center of the Earth

Where;
Xcm is the distance from center of the Earth =?
Me is the mass of the Earth = 6 × 10²⁴ kg
Xe is the center mass of the Earth = 0
Mm is the mass of the moon = 7 × 10²² kg
Xm is the center mass of the moon = 4 × 10⁸ m

Therefore, the center of mass of the Earth–Moon system is 4.613 × 10⁶ m from center of the Earth.