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Mazyrski [523]
3 years ago
13

What volume of water at 0 ∘C can a freezer make into ice cubes in 1.5 h , if the coefficient of performance of the cooling unit

is 9.0 and the power input is 1.2 kilowatt? Express your answer using two significant figures.
Physics
1 answer:
Sophie [7]3 years ago
4 0

Answer:

1.7\times 10^{-1}\ m^3

Explanation:

\rho = Density of water = 1000 kg/m³

Mass is given by

m=\rho V\\\Rightarrow m=1000V

Q=mL\\\Rightarrow Q=1000V336000\\\Rightarrow Q=336\times 10^{6}V

Energy used is

9\times 1200=10800\ W

Q=10800\times 1.5\times 3600=58320000\ J

336\times 10^{6}V=58320000\\\Rightarrow V=\dfrac{58320000}{336\times 10^{6}}\\\Rightarrow V=0.173571428571\ m^3

The volume of water is 1.7\times 10^{-1}\ m^3

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3 years ago
Read 2 more answers
A test charge of +2μC is placed halfway between a charge of +6μC and another of +4μC separated by 10 cm. (a) What is the magnitu
Nady [450]

Answer:

Part a)

F = 14.4 N

Part b)

away from +6μC charge

Explanation:

Force on the charge placed midway between two charges is given by

F = \frac{kq_1q}{r^2} - \frac{kq_2q}{r^2}

here we know that

q = 2\mu C

q_1 = 6 \mu C

q_2 = 4\mu C

here the charge is placed at mid point so we have

r = 5 cm

now we have

F = \frac{(9\times 10^9)(6\mu C)(2\mu C)}{0.05^2} - \frac{(9\times 10^9)(2\mu C)(4\mu C)}{0.05^2}

F = 43.2 - 28.8 = 14.4 N

Part b)

since +6μC charge is more in magnitude so the force due to this charge will be more so the net force on it is away from +6μC charge

8 0
4 years ago
A friend says that the reason one's hair stands out while touching a charged Van de Graaff generator is simply that the hair str
Llana [10]

Answer:

Explanation:

Yes I agree with the statement .

When a person who is perfectly insulated from the earth , touches a Van de Graaff , his body acquires charge . when the hair acquires it, it stands out due to mutual repulsion . It is to be noted here that at pointed areas on a surface , there is larger accumulation of charge. Accumulation of charge is greater at hair tops .

It is also a general observation that when a bird sits on high tension wire , his feather stands out due to the same reason.

5 0
3 years ago
If you were in charge of designing a wire to carry electricity across your city, state or province, which of
Anon25 [30]

Answer:

Thin, aluminium and buried underground.

Explanation:

When it comes to electrification of a state or province, some characteristics of the wire to use must be considered. This would help to minimize and avoid power loss and wire burns.

i. The wire to use should be thin, and a quite number can be twisted one against the other so as to increase the surface area for heat dissipation.

ii. Aluminium wire is more preferable for this project. It has a high melting point, and reduces energy loss.

iii. Burying the wire underground through an insulator is the best choice, though expensive but would preserve the wire from external influence.

7 0
3 years ago
Why does a properly adjusted head restraint help prevent head and neck injuries to occupants in rear-end collisions? Explain you
hammer [34]
When a car hits you in a rear end collision, the car initially has a momentum going in one direction. This causes your car to move in the same direction that car was moving even if you were at rest. So, for conservation of momentum, you initially have momentum going in the east direction for example, after the collision, you will have a change in momentum which causes you to have a velocity in the west direction. This is because you are initially at rest and then there is a sudden change in velocity so when you speed up, that momentum causes you to move backwards. If you don't have a properly adjusted neckrest you could may experience whiplash.
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