Image of the plate is missing, so i have attached it.
Answer:
A) t = 7.854 mm
B) σ = 26.67 MPa
Explanation:
A) From shearing of rivet, formula for pressure is;
P = τ•A_rivets
Where;
τ is allowable stress
A_rivets is Area of rivet
We are given:
τ = 60 MPa
Diameter; d = 20 mm
A_rivets = πd²/4 = π × 20²/4 = 100π
Thus;
P = 60 × 100π
P = 6000π N
From bearing of plate material, we can calculate pressure as;
P = σ_b•A_b
We are given;
σ_b = 120 MPa
A_b is area of plate = 20t
Where t is the thickness
Thus;
6000π = 120 × 20t
t = 6000π/(120 × 20)
t = 7.854 mm
B) Largest average tensile stress is given by the formula;
σ = P/A
Where A = 110t - 20t
A = 90t
A = 90 × 7.854
Thus;
σ = 6000π/(90 × 7.854)
σ = 26.67 MPa
Explanation:
velocity of disc 
lets call (h) 1 m to make it simple.
= 3.614 m/s
m/s pointing towards this:
velocity of hoop=
lets call (h) 1m to make it simple again.
m/s
![\sqrt(gh) = sqrt(hg)so [tex]4×V_d= \sqrt(4/3hg)V_h=\sqrt(hg)](https://tex.z-dn.net/?f=%5Csqrt%28gh%29%20%3D%20sqrt%28hg%29%3C%2Fp%3E%3Cp%3Eso%20%5Btex%5D4%C3%97V_d%3D%20%5Csqrt%284%2F3hg%29V_h%3D%5Csqrt%28hg%29)
The disc is the fastest.
While i'm on this subject i'll show you this:
Solid ball 
solid disc 
hoop 
The above is simplified from linear KE + rotational KE, the radius or mass makes no difference to the above formula.
The solid ball will be the faster of the 3, like above i'll show you.
solid ball: velocity 
let (h) be 1m again to compare.
m/s
solid disk speed
uniform hoop speed 
solid sphere speed
Answer:
28.7 m at 46.9°
Explanation:
The x component of the displacement is:
x = 6 m cos 0° + 25 m cos 57°
x = 19.6 m
The y component of the displacement is:
y = 6 m sin 0° + 25 m sin 57°
y = 21.0 m
The total displacement is found with Pythagorean theorem:
d = √(x² + y²)
d = 28.7 m
And the direction is found with trig:
θ = tan⁻¹(y/x)
θ = 46.9°
Newton's law of universal gravitation gives the gravitational force between two objects:
F = GMm/r²
F = gravitational force, G = gravitational constant, M & m are the masses of the two objects, r = distance between the objects
