Answer:
D. 130 J
Explanation:
The coefficient of performance for a machine that is being used to cool, is given by:

Here
is the heat removed from the cold reservoir, W is the work required, that is, the energy required to remove the heat from the interior of the house,
is the cold temperature and
is the hot temperature. Recall use absolutes temperatures(
). Replacing and solving for W:

The power is 833.3 W
Explanation:
First of all, we need to calculate the work done in lifting the barbell, which is equal to the change in gravitational potential energy of the barbell:

where
mg = 1250 N is the weight of the barbell
h = 2 m is the change in height
Substituting,

Now we can calculate the power, which is equal to the work done per unit time:

where
W = 2500 J is the work done
t = 3 s is the time taken
Substituting,

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72 m/s
Explanation:
Given,
Frequency ( f ) = 6 Hz
Wavelength ( λ ) = 12 m
To find : -
Speed ( v ) = ?
Formula : -
v = f x λ
v
= 6 x 12
= 72 m/s
Therefore,
the speed of a wave with a frequency of 6 Hz and a wavelength of 12 m is 72 m/s.
Answer:
Capacitance is 0.572×10⁻¹⁰ Farad
Explanation:
Radius = R₁ = 6.25 cm = 6.25×10⁻² m
Radius = R₂ = 15 cm = 15×10⁻² m
Dielectric constant = k = 4.8
Electric constant = ε₀ = 8.854×10⁻¹² F/m
ε/ε₀=k
ε=kε₀

∴ Capacitance is 0.572×10⁻¹⁰ Farad