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Umnica [9.8K]
3 years ago
8

An object is placed 250 cm in front of a concave circular mirror, and the image of the object also appears at 250 cm in front of

the mirror. What is the radius of curvature of the mirror?
500 cm
125 cm
25.0 cm
250 cm
Physics
1 answer:
Scrat [10]3 years ago
3 0

Answer:

Radius of curvature of the mirror = 250 cm

Explanation:

Given:

Object distance from mirror = 250 cm (u=-250)

Object distance appears in mirror = 250 cm (v=-250)

Find:

Radius of curvature of the mirror

Computation:

Using mirror formula

1/f = 1/v + 1/u

1/f = 1/(-250) + 1/(-250)

f = (-250/2)

f = -125 cm or 125 cm

Radius of curvature of the mirror = 2(f)

Radius of curvature of the mirror = 2(125)

Radius of curvature of the mirror = 250 cm

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Water is poured into a bowl at a constant rate of 17.0 cm^3/s. The bowl has a circular cross section, but does not have a unifor
7nadin3 [17]

Answer:

10.29 cm/s

Explanation:

Discharge in to the bowl = 17.0 cm³/s

Diameter of the bowl, d₁ = 1.45 cm

Now,

Rate at which water level rise at its diameter = \frac{\textup{Discharge}}{\textup{Area of cross-section}}

also,

Area of cross-section = \frac{\pi}{\textup{4}}\times1.45^2

or

Area of cross-section = 1.651 cm²

Therefore,

Rate at which water level rise at its diameter = \frac{\textup{17}}{\textup{1.651}}

or

Rate at which water level rise at its diameter = 10.29 cm/s

8 0
4 years ago
Air at 3 104 kg/s and 27 C enters a rectangular duct that is 1m long and 4mm 16 mm on a side. A uniform heat flux of 600 W/m2 is
ad-work [718]

Answer:

T_{out}=27.0000077 ºC

Explanation:

First, let's write the energy balance over the duct:

H_{out}=H_{in}+Q

It says that the energy that goes out from the duct (which is in enthalpy of the mass flow) must be equals to the energy that enters in the same way plus the heat that is added to the air. Decompose the enthalpies to the mass flow and specific enthalpies:

m*h_{out}=m*h_{in}+Q\\m*(h_{out}-h_{in})=Q

The enthalpy change can be calculated as Cp multiplied by the difference of temperature because it is supposed that the pressure drop is not significant.

m*Cp(T_{out}-T_{in})=Q

So, let's isolate T_{out}:

T_{out}-T_{in}=\frac{Q}{m*Cp}\\T_{out}=T_{in}+\frac{Q}{m*Cp}

The Cp of the air at 27ºC is 1007\frac{J}{kgK} (Taken from Keenan, Chao, Keyes, “Gas Tables”, Wiley, 1985.); and the only two unknown are T_{out} and Q.

Q can be found knowing that the heat flux is 600W/m2, which is a rate of heat to transfer area; so if we know the transfer area, we could know the heat added.

The heat transfer area is the inner surface area of the duct, which can be found as the perimeter of the cross section multiplied by the length of the duct:

Perimeter:

P=2*H+2*A=2*0.004m+2*0.016m=0.04m

Surface area:

A=P*L=0.04m*1m=0.04m^2

Then, the heat Q is:

600\frac{W}{m^2} *0.04m^2=24W

Finally, find the exit temperature:

T_{out}=T_{in}+\frac{Q}{m*Cp}\\T_{out}=27+\frac{24W}{3104\frac{kg}{s} *1007\frac{J}{kgK} }\\T_{out}=27.0000077

T_{out}=27.0000077 ºC

The temperature change so little because:

  • The mass flow is so big compared to the heat flux.
  • The transfer area is so little, a bigger length would be required.
3 0
3 years ago
For the winter, a duck flies 10.0 m/s due south against a gust of wind with a speed of 2.5 m/s. What is the resultant velocity o
Sati [7]
10.0 m/s + (-2.5 m/s) = 7.5 m/s
6 0
4 years ago
Helppppppppppppppp.......
kow [346]

Answer:

9013 m/s

Explanation:

hope it helped!!!

8 0
3 years ago
Which of these describe the composition of earths atmosphere?
Alja [10]
Earth's atmosphere is a <em>mixture</em> of gases that have
not reacted to become chemical compounds.
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3 years ago
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