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3 years ago

13

High friction materials

1 answer:

Harrizon [31]3 years ago

7 0

Answer:

For the dry and static friction materials, some of these are Rubber, Aluminum, Gold, Platinum,

Explanation:

High friction materials has higher coefficient of friction (COF).

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Phương trình trạng thái tổng quát của khí lí tưởng diễn tả là

tatyana61 [14]

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pV/T=const goodluke

6 0

3 years ago

An object of irregular shape has a characteristic length of L = 0.5 m and is maintained at a uniform surface temperature of Ts =

goblinko [34]

Answer:

The value of the average convection coefficient is 20 W/Km².

Explanation:

Given that,

For first object,

Characteristic length = 0.5 m

Surface temperature = 400 K

Atmospheric temperature = 300 K

Velocity = 25 m/s

Air velocity = 5 m/s

Characteristic length of second object = 2.5 m

We have same shape and density of both objects so the reynold number will be same,

We need to calculate the value of the average convection coefficient

Using formula of reynold number for both objects

$R_{1}=R_{2}$

$\dfrac{u_{1}L_{1}}{\eta_{1}}=\dfrac{u_{2}L_{2}}{\eta_{2}}$

$\dfrac{h_{1}L_{1}}{k_{1}}=\dfrac{h_{2}L_{2}}{k_{2}}$

Here, $k_{1}=k_{2}$

$h_{2}=h_{1}\times\dfrac{L_{1}}{L_{2}}$

$h_{2}=\dfrac{q}{T_{2}-T_{1}}\times\dfrac{L_{1}}{L_{2}}$

Put the value into the formula

$h_{2}=\dfrac{10000}{400-300}\times\dfrac{0.5}{2.5}$

$h_{2}=20\ W/Km^2$

Hence, The value of the average convection coefficient is 20 W/Km².

7 0

4 years ago

You have a tungsten sphere (emissivity ε = 0.35) of radius 25 cm at a temperature of 25°C. If the sphere is enclosed in a room w

egoroff_w [7]

Answer:

Explanation:

Stefan's formula for emission of radiation is

E = e σ A ( T⁴ - T₀⁴ )

E is energy radiated , e is emissivity , σ is stefan's constant , T is temperature of object and T₀ is temperature of surrounding. A is area of surface .

E = .35 x 5.67 x 10⁻⁸ ( 298⁴ - 268⁴ ) x 4π x .25²

= 1.9845 x 10⁻⁸ ( 78.86 - 51.58 ) x 10⁸ x .0625

= 3.38 J /s

8 0

3 years ago

A ball of mass 2 kg is kept on the hill of height 3 km. Calculate the potential energy possessed by it ?

zysi [14]

We know that -

$P.E=m*g*h$

Where,

$m = mass$

$g = acceleration$ $due$ $to$ $gravity$

$h=height$

First we convert height into meters.

1 km = 1000 meters

3 km = 1000 * 3 meters = 3000 meters

So, putting the values in the above formula, and by taking 'g' = 9.8 m/s², we get-

$P.E.= 2*3000*9.8$

$P.E.= 58800$ $Joules$

$P.E.= 58.8$ $kJ$

7 0

3 years ago

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denis23 [38]

Answer:

its y

Explanation:

3 0

3 years ago