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Genrish500 [490]
1 year ago
6

Consider an acrylic sheet of thickness L = 5 mm that is used to coat a hot, isothermal metal substrate at Th = 300°C. The proper

ties of the acrylic are rho = 1990 kg/m3, c = 1470 J/kg · K, and k = 0.21 W/m · K. Neglecting the thermal contact resistance between the acrylic and the metal substrate, determine how long it will take for the insulated back side of the acrylic to reach its softening temperature, Tsoft = 90°C. The initial acrylic temperature is Ti = 20°C.

Physics
1 answer:
Ad libitum [116K]1 year ago
7 0

Answer:

74.52s

Explanation:

The solution is shown in the picture below

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A girl rolls a ball up an incline and allows it to re- turn to her. For the angle and ball involved, the acceleration of the bal
zalisa [80]

Answer:

3.28 m

3.28 s

Explanation:

We can adopt a system of reference with an axis along the incline, the origin being at the position of the girl and the positive X axis going up slope.

Then we know that the ball is subject to a constant acceleration of 0.25*g (2.45 m/s^2) pointing down slope. Since the acceleration is constant we can use the equation for constant acceleration:

X(t) = X0 + V0 * t + 1/2 * a * t^2

X0 = 0

V0 = 4 m/s

a = -2.45 m/s^2 (because the acceleration is down slope)

Then:

X(t) = 4*t - 1.22*t^2

And the equation for speed is:

V(t) = V0 + a * t

V(t) = 4 - 2.45 * t

If we equate this to zero we can find the moment where it stops and begins rolling down, that will be the highest point:

0 = 4 - 2.45 * t

4 = 2.45 * t

t = 1.63 s

Replacing that time on the position equation:

X(1.63) = 4 * 1.63 - 1.22 * 1.63^2 = 3.28 m

To find the time it will take to return we equate the position equation to zero:

0 = 4 * t - 1.22 * t^2

Since this is a quadratic equation it will have to answers, one will be the moment the ball was released (t = 0), the other will eb the moment when it returns:

0 = t * (4 - 1.22*t)

t1 = 0

0 = 4 - 1.22*t2

1.22 * t2 = 4

t2 = 3.28 s

7 0
1 year ago
Water is pumped from a lower reservoir to a higher reservoir by a pump that provides 20 kW of shaft power. The free surface of t
kifflom [539]

Answer:

6.5 kW

Explanation:

Input power = 20 kW = 20000 W

h = 45 m

Volume flow per second = 0.03 m^3 /s

mass flow per second = volume flow per second x density of water

                                    = 0.03 x 1000 = 30 kg/s

Output power = m g h / t = 30 x 10 x 45 = 13500 W

Power converted in form of heat = Input power - Output power

                                                       = 20000 - 13500 = 6500 W = 6.5 kW

Thus, mechanical power converted into heat is 6.5 kW.

7 0
2 years ago
Hippos spend much of their lives in water, but amazingly, they don’t swim. manatees, They have, like little very body fat. The d
kenny6666 [7]

Answer:

428.59 N

Explanation:

Buoyant force, B=Vg\rho where V is volume, g is gravitational constant and \rho is density

B+F_{upward}=mg where F_{upward} is upward force

Vg\rho_{w}+F_{upward}=mg

F_{upward}=mg- Vg\rho_{w}

F_{upward}=g(mg- V\rho_{w})=g(m-m\frac {\rho_{w}{\rho_{hippo}} where \rho_{hippo} is the density of hippo

F_{upward}=mg(1-\frac {\rho_{w}}{\rho_{hippo}})

Using g as 9.81

F_{upward}=1500*9.81*(1-1000/1030)= 428.5922 N

Therefore, the upward force=428.59 N

3 0
2 years ago
A solid sphere of brass (bulk modulus of 14.0 ✕ 1010 N/m2) with a diameter of 2.20 m is thrown into the ocean. By how much does
astra-53 [7]

Answer:

Diameter decreases by the diameter of 0.0312 m.

Explanation:

Given that,

Bulk modulus =  14.0 × 10¹⁰ N/m²

Diameter d = 2.20 m

Depth = 2.40 km

Pressure = ρ g h = 1030 × 9.81 × 2.4 × 1000

               = 24.25 × 10⁶  N/m²

Volume = \dfrac{4}{3} \pi r^3

         \dfrac{\Delta V}{V}=\dfrac{(\Delta r)^3}{r^3}

Bulk modulus is equal to

B = -\dfrac{\Delta P}{\dfrac{\Delta V}{V} }

now

B = -\dfrac{24.25 \times 10^6}{\dfrac{(\Delta r)^3}{r^3} }

B = -\dfrac{24.25 \times 10^6}{\dfrac{(\Delta r)^3}{1.1^3} }

(\Delta r)^3 = \dfrac{24.25 \times 10^6 \times 1.1^3}{14.0 \times 10^{10}}

Δ r = -0.0156 m

change in diameter

Δ d = -2 × 0.0156

Δ d = -0.0312 m

Diameter decreases by the diameter of 0.0312 m.

7 0
1 year ago
Suppose a person has a small intestine that has fewer villi than normal. Would the person most likely be overweight or underweig
Mekhanik [1.2K]
They would be likely to be underweight. This is because the role of villi is to increase absorption of soluble molecules, they do this by increasing surface area for absorption to occur across.
If the person has less villi than normal in their small intestine, then the surface area will not be as large meaning there is less area for absorption to occur across so less soluble molecules will be absorbed.
4 0
1 year ago
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