Answer:
time required for cooling process = 0.233 hours
Explanation:
In Transient heat conduction of a Sphere, the formula for Biot number is;
Bi = hL_c/k
Where L_c = radius/3
We are given;
Diameter = 12mm = 0.012m
Radius = 0.006m
h = 20 W/m²
k = 40 W/m·K
So L_c = 0.006m/3 = 0.002m
So,Bi = 20 x 0.002/40
Bi = 0.001
The formula for time required is given as;
t = (ρVc/hA)•In[(T_i - T_(∞))/(T - T_(∞))]
Where;
A is Area = πD²
V is volume = πD³/6
So,
t = (ρ(πD³/6)c/h(πD²))•In[(T_i - T_(∞))/(T - T_(∞))]
t = (ρDc/6h)•In[(T_i - T_(∞))/(T - T_(∞))]
We are given;
T_i = 1200K
T_(∞) = 300K
T = 450K
ρ = 7800 kg/m³
c = 600 J/kg·K
Thus, plugging in relevant values;
t = (7800 x 0.012 x 600/(6 x20) )•In[(1200 - 300)/(450 - 300)]
t = 468•In6
t = 838.54 seconds
Converting to hours,
t = 838.54/3600
t = 0.233 hours
Answer:
D. Rectangular
Explanation:
This is because rectangular coordinate systems are used in plotting common straight lines graphs with the formulae,
Y = Mx + c
Where y is the vertical coordinate
X is the horizontal coordinate
M is the dlope of the line
C is the y-axis intercept
The employer must inform employees and their representatives of their right to examine and copy all abatement documents submitted to the Agency. ... The employer must comply with an employee's or employee representative's request to examine and copy abatement documents within 5 working days of receiving the request.
Answer:
The material that is not used for wood sanding is
3. Emery
Explanation:
The materials recommended for use as materials for wood sanding includes;
1) Garnet paper is a very brittle moderately hard, self sharpening and durable material which is a popular choice of most woodworkers
2) Aluminum oxide is used for the sanding of hardwood
3) Emery is used for the smoothening of a metal surface
4) Silicon carbide has a faster effect rate than aluminum oxide, and it is used to smoothen woodwork objects
Therefore, the material that is not used for wood sanding is Emery