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2 answers:
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Answer:
a) W = 180.87 J , b) ΔU = -180.87 J , c) ΔU = -180.87 J
Explanation:
a) Work is defined as
W = F .ds
Where bold indicates vectors, we can write the scalar product
W = F s cos θ
Where the angle is between force and displacement.
The force of gravity is the weight of the body, which is directed downwards and the displacement thickens the tip of the cliff at the bottom, so that it is directed downwards, therefore the angle is zero degrees
W = y
W = m g y
For this problem we must fix a reference system, from the statement it is established that the system is placed at the base of the cliff, so that final height is zero and the initial height (y₀ = 7.69m)
W = 2.40 9.8 (7.69-0)
W = 180.87 J
b) The potential energy is
U = mg y
The change in potential energy,
ΔU = - U₀
ΔU = mg (- y₀)
ΔU = 2.4 9.8 (0 -7.69)
ΔU = -180.87 J
c) in this case we change the reference system to the height of the cliffs, for this configuration
y₀ = 0
= -7.69 m
ΔU = 2.4 9.8 (-7.69 -0)
ΔU = -180.87 J
Answer:
Therefore,
We can use Computer to surf internet for 5.7 hours.
Explanation:
Given:
For Clothes Dryer,
Current, I = 14 A
Voltage, V = 240 V
Time, t = 33 min = 33 × 60 = 1980 s
For Computer,
Current, I = 2.7 A
Voltage, V = 120 V
To Find:
Time, t = ? For Computer to surf with the Energy of Clothes Dryer,
Solution:
According to Joule's Law, Energy in joules for voltage "V" and Current "I" for time "t" second is given as,
For Clothes Dryer
Substituting the values we get
Now for Computer we have E = 6652.8 kJ, then time will be
Again we have,
Substituting the values we get
Time in Minutes,
Time in hours again we have to divide minutes by 60
Therefore,
We can use Computer to surf internet for 5.7 hours.