The cost of boiling 500 cm³ of water using the 3 KW Kettle is 1.35p
<h3>What is power? </h3>
This is defined as the rate in which energy is consumed. Electrical power is expressed mathematically as:
Power (P) = Energy (E) / time (t)
P = E / t
<h3>How to determine the energy</h3>
- Power (P) = 3 KW
- Time (t) = 3 mins = 3 / 60 = 0.05 h
- Energy (E) =?
E = Pt
E = 3 × 0.05
E = 0.15 KWh
<h3>How to determine the cost</h3>
- Energy (E) = 0.15 KWh
- Cost per unit = 9p
- Cost =?
Cost = Energy × cost per unit
Cost = 0.15 × 9
Cost = 1.35p
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<span>............D. Elliptical</span>
Yes, the volume of the cylinder will remain constant. As the radius decreases, the height will increase to make sure that the volume is kept the same.
We have been given a value of dr/dt and are required to find dh/dt
Because the volume is constant, we can plug it into the formula for the volume of the cylinder and rearrange it to make h the subject:
128 = πr²h
h = 128/πr²
Now we differentiate both sides:
dh/dr = -256/πr³
Applying the chain rule:
dh/dt = dh/dr x dr/dt
dh/dt = (-256/πr³) x -0.05
dh/dt = 64/5πr³; substituting the value of r
dh/dt = 64/5π(1.5)³
dh/dt = 1.21 in/sec
Answer:
sun is the main source while the other object reflect light on the sun
Explanation:
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