Answer:
a. The radius r = 5.42 cm and the height h = 10.84 cm
b. 553.73 cm²
c. i. Beauty ii. Design
Explanation:
a. What would be the optimal dimensions (radius and height) to minimize surface area?
The volume of the standard container is a cylinder and its volume is V = πr²h where r = radius of container and h = height of container.
Since V = 1000 cm³,
1000 cm³ = πr²h (1)
Now, the surface area of a cylinder is A = 2πr² + 2πrh where r and h are the radius and height of the cylinder.
From (1), h = 1000/πr².
Substituting h into A, we have
A = 2πr² + 2πrh
A = 2πr² + 2πr(1000/πr²)
A = 2πr² + 2000/r
To maximize A, we differentiate A with respect to r and equate to zero to find the value of r at which A is maximum.
So, dA/dr = d[2πr² + 2000/r]/dr
dA/dr = d[2πr²]/dr + d[2000/r]/dr
dA/dr = 4πr - 2000/r²
Equating the equation to zero, we have
4πr - 2000/r² = 0
4πr = 2000/r²
r³ = 2000/4π
r = ∛(1000/2π)
r = 10(1/∛(2π))
r = 10(1/∛(6.283))
r = 10/1.8453
r = 5.42 cm
To determine if this value of r gives a minimum for A, we differentiate dA/dr with respect to r.
So, d(dA/dr)/dr = d²A/dr²
= d[4πr - 2000/r²]/dr
= d[4πr]/dr - d[2000/r²]/dr
= 4π + 4000/r³
Substituting r³ = 2000/4π into the equation, we have
d²A/dr² = 4π + 4000/r³ = 4π + 4000/(2000/4π) = 4π + 2 × 4π = 4π + 8π = 12π > 0
Since d²A/dr² = 12π > 0, then r = 5.42 cm gives a minimum for A.
Since h = 1000/πr²
h = 1000/π(5.42)²
h = 1000/92.288
h = 10.84 cm
So, the radius r = 5.42 cm and the height h = 10.84 cm
b. What would the surface area be?
Since the surface area, A = 2πr² + 2πrh
Substituting the values of r and h into A, we have
A = 2πr² + 2πrh
A = 2πr(r + h)
A = 2π5.42(5.42 + 10.84)
A = 10.84π(16.26)
A = 176.2584π
A = 553.73 cm²
c. Suggest at least two reasons why this is different from the ice cream packaging that you see in the stores.
i. Beauty
ii. Design