32 days bcz 1250 meters took 120 hours (120 hrs=5 days) so 8000 m will take: 8000x120/1250= 768 hrs
782 hrs/24= 32 days
Step-by-step explanation:
first of all, your teacher wrote nonsense in the answer options : an area is always given in squared units. never in cubed units (which would be volume).
the area is : 1/2 × perimeter × apothem
the perimeter is simply 12 × 5 = 60 meters.
apothem = (a/2)×cot(pi/12) = 5/2 × cot(pi/12) =
= 9.330127019... meters
so the area is
1/2 × 60 × 9.330127019... = 279.9038106... m²
therefore, the third answer option is correct (although it is m², and not m³).
by the way, you have question 3 wrong. I answered this with the correct apothem calculation in the explanation for question 4.
Answer:
15mm
Step-by-step explanation:
we are looking for extension
To get Extension you need the original length and the strain both of which you are given
initial length L = 1.00m
the area A = 0.5mm² = 0.5 mm² = 0.5 x 10⁻⁶ m² ( we are changing to metres squared)
E = 2.0 x 10¹¹ n/m², Young's modulus
P = 1500N, the applied tension
Now to Calculate the stress.
σ = P/A (force/area) = (1500 N)/(0.5 x 10⁻⁶ m²) = 3 x 10⁹ N/m²
Also, Let β = the stretch of the string.
Then the strain is
ε = β/L (extension/ original length)
By definition, the strain is ε = σ/E = (3 x 10⁹ N/m²)/(2 x 10¹¹ N/m²) = 0.015
Therefore β/(1 m) = 0.015β = 0.015 m = 15 mm
Answer: 15 mm
