A 45.0-kg person steps on a scale in an elevator. The scale reads 460 n. What is the magnitude of the acceleration of the elevat
1 answer:
Answer:
Explanation:
There are two forces acting on the person as he's standing on the scale in the elevator:
- Its weight, , downward, with m = 45.0 kg being his mass and g = 9.8 m/s^2 being the acceleration of gravity
- The normal reaction exerted by the scale on the person, N, upward, which is equal to the value read on the scale, N = 460 N
Using Newton's second law, we can write
Where a is the acceleration of the person (and of the elevator). Solving for a,
And since we chose positive as the upward direction, the acceleration is upward.
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Answer:
The answers to the question are
(i) The rate of heat loss per-unit-length (W/m) from the pipe is 131.62 W
(ii) The temperature of the outer surface of the insulation is 49.89 °C
Explanation:
To solve the question, we note that the heat transferred is given by
Where
= Temperature at the inside of the pipe = 300 °C
= Temperature at the outside of the pipe = 20 °C
r₁ =internal radius of pipe = 4.0 cm
r₂ = Outer radius of pipe = 4.5 cm
r₃ = Outer radius of the insulation = r₂ + 2.5 = 7.0 cm
= 15 W/m·K
= 0.038 W/m·K
= 75 W/m²·K
= 10 W/m²·K
Plugging in the values in the above equation where for a unit length L = 1 m, we have
Q = 131.32 W
From which we have, for the film of air at the pipe outer boundary layer
Where
for the air film on the pipe outer surface is given by
where A =area of the outside of the pipe
= = 0.227 K/W
Therefore
131.32 W = which gives
= 49.89 °C
Heat transferred by radiation = q' = ε×σ×(T₁⁴ - T₂⁴)
Where ε = 0.9, σ, = 5.67×10⁻⁸W/m²·(K⁴)
T₁ = Surface temperature of the pipe = 49.89 °C and
T₂ = Temperature of the surrounding = 20.00 °C
Plugging in the values gives, q' = 0.307 W per m²
Total heat lost per unit length = 131.32 + 0.307 =131.62 W
The force of attraction between the opposite charges of the ions in an ionic compound is an ionic bond.
<u>Explanation:</u>
The transfer process of valence electron between atoms referred as ionic bond. This is a kind of chemical bonds which can create two oppositely charged ions. In the presence of ionic bonds, the metal loses electrons and becomes a positive charge cation, while non-metal accepts these electrons and becomes a negative charge anion.
Here, more than 1 electron can be emitted or received to meet the octet principle and the net charge of the compound should be zero. For example: Table salt. In this compound, sodium loses the electron to become , while the chlorine loses the electron to become
.