Answer:
60 km/h
Explanation:
In the first part of the trip, the speed is
v = 80 km/h
while the time interval is
t = 3 h
So, the distance covered is:
d = vt = (80)(3)= 240 km
The problem states that this distance is half distance between home and the destination - so, the total distance between home and the destination is

The time taken to cover the second part of the trip is 5 h, so the total time taken is
T = 3 h + 5 h = 8 h
Therefore, the average velocity for the entire trip is

Answer:
a. I = 30 A
b. E = 1080000 J = 1080 KJ
c. ΔT = 12.86°C
d. Cost = $ 4.32
Explanation:
a.
The current in the coil is given by Ohm's Law:

where,
I = current = ?
V = Voltage = 120 V
R = Resistance = 4 Ω
Therefore,

<u>I = 30 A</u>
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b.
The energy can be calculated as:

<u>E = 1080000 J = 1080 KJ</u>
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c.
For the increase in the temperature of water:

where,
m = mass of water = 20 kg
C = specific heat of water = 4.2 KJ/kg.°C
Therefore,

<u>ΔT = 12.86°C</u>
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d.
First, we will calculate the total energy consumed:

Now, for the cost:

<u>Cost = $ 4.32</u>
In this case, the air from the warm area will always start moving towards the colder areas because as the temperature in both lands should be equal. This is one of the laws of thermodynamics.