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ioda
3 years ago
8

The freezer compartment in a conventional refrigerator can be modeled as a rectangular cavity 0.3 m high and 0.25 m wide with a

depth of 0.5 m. Determine the thickness of styrofoam insulation (k = 0.30 W/m⋅K) needed to limit the heat loss to 400 W if the inner and outer surface temperatures are −10 and 33°C, respectively.
Physics
1 answer:
Mkey [24]3 years ago
3 0

Answer:

Thickness of Styrofoam insulation is 0.02741 m.

Explanation:

Given that,

Height = 0.25 m

Depth = 0.5 m

Power = 400 W

Temperature = 33°C

We need to calculate the area of Styrofoam

Using formula of area

A=2(lb+bh+hl)

Put the value into the formula

A=2(0.3\times0.5+0.25\times0.5+0.5\times0.3)

A=0.85\ m^2

Inner surface temperature of freezer

T_{i}=-10°C=263\ K

Outer surface temperature of freezer

T_{o}=33+273=306\ K

We need to calculate the thickness of Styrofoam insulation

Using Fourier law,

q=\dfrac{kA}{L}(T_{o}-T_{i})

L=\dfrac{kA}{q}(T_{o}-T_{i})

Put the value into the formula

L=\dfrac{0.30\times0.85}{400}(306-263)

L=0.02741\ m

Hence, Thickness of Styrofoam insulation is 0.02741 m.

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Suppose that the acceleration of a model rocket is proportional to the difference between 100 ft/sec and the rocket's velocity.
sp2606 [1]

Answer:

Explanation:

initial velocity, u = 0

final velocity, v = 80 ft/s

acceleration, a = 150 ft/s²

Let the time taken is t.

v = u + at

80 = 0 + 150 x t

t = 0.53 second

3 0
3 years ago
- How much force is needed to accelerate a 26 kg skier at 4 m/sec??
kondor19780726 [428]

Answer:

<h2>104 N</h2>

Explanation:

The force acting on an object given it's mass and acceleration can be found by using the formula

force = mass × acceleration

From the question we have

force = 26 × 4

We have the final answer as

<h3>104 N</h3>

Hope this helps you

8 0
2 years ago
The gravitational potential energy of a particle of mass m moving under the influence of a fixed mass M is given by - , where G
djverab [1.8K]

-GMm/2r is the total energy of the mass m if it is in a circular orbit about mass M.

Given

A particle of mass m moving under the influence of a fixed mass's M, gravitational potential energy of formula  -GMm/r, where r is the separation between the masses and G is the gravitational constant of the universe.

As the Gravity Potential energy of particle = -GMm/r

Total energy of particle = Kinetic energy + Potential Energy

As we know that

Kinetic energy = 1/2mv²

Also, v is equals to square root of GM/r

v = √GM/r

Put the value of v in the formula of kinetic energy

We get,

Kinetic Energy = GMm/2r

Total Energy = GMm/2r + (-GMm/r)

                     = GMm/2r - GMm/r

                     = -GMm/2r

Hence, -GMm/2r is the total energy of the mass m if it is in a circular orbit about mass M.

Learn more about Gravitational Potential Energy here brainly.com/question/15896499

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3 0
1 year ago
Electronic flash units for camera contain a capacitor for storing the energy used to produce the flash. In one such unit, the fl
nadezda [96]

Answer:

420J

Explanation:

Power is the time rate of change in energy. Power is the ratio of energy to time. The S.I unit of power is in watts.

Given that the flash lasts for 1/675 s, power output is 2.7 * 10⁵ W. Hence:

Power = Energy / time

Substituting:

2.7 * 10⁵ W = Energy / (1/675)

Energy = 2.7 * 10⁵ W * 1/675 = 400J

Therefore the energy emitted as light is 400J.

Since the conversion of electric energy to light is 95% efficient, hence the energy stored as electrical energy is:

Energy(capacitor) = 5% of 400J + 400J = 0.05*400 + 400

Energy(capacitor) = 420J

8 0
2 years ago
A long solenoid of radius 3 cm has 1100 turns per meter. If the solenoid carries a current of 1.5 A, then calculate the magnetic
Arada [10]

Answer:

The magnetic field at the center of the solenoid is 2.1  × 10⁻³ T

Explanation:

The magnetic field B at the center of the solenoid is given by

B = μ₀ni where μ₀ = permeability of free space = 4π × 10⁻⁷H/m, n = number of turns per unit length of the solenoid = 1100 turns per meter and i = current in the solenoid = 1.5 A.

So B = μ₀ni

= 4π × 10⁻⁷H/m × 1100 × 1.5 A

= 4π × 10⁻⁷H/m × 1650 A-turns/m

= 20734.5 × 10⁻⁷T  

= 2.07345 × 10⁻³ T

≅ 2.1  × 10⁻³ T

So the magnetic field at the center of the solenoid is 2.1  × 10⁻³ T

3 0
3 years ago
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