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3 years ago

Every year _______ species go extinct. a. 3 b. 72 c. 1000 d. 20000

2 answers:

7 0

Well, the thing is: we don't really know, as we don't even know how many species there are on earth.

If we take a look at the estimates of <span>World Wide Fund for Nature, an organization that works toward combating species extinction, their estimates vary from 200 to 100 000 - but a probable number is 20 000 (d). </span>
<span />

schepotkina [342]3 years ago

6 0

Answer:

d. 20000

Explanation:

It has been observed that over the years, species have been going extinct due to human reasons such as excessive hunting, environmental factors such as natural disasters, global warming and also due to changes in their genetic makeup or a reduced reproduction.

It has been estimated that every year 20,000 species are going extinct.

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Most asteroids lie between the orbits of

Anika [276]

I believe the answer is B. that's where the asetroid belt is.

4 0

3 years ago

Read 2 more answers

A counterflow double-pipe heat exchanger is used to heat water from 20°C to 80°C at a rate of 1.2 kg/s. The heating is to be com

bixtya [17]

Answer:L=109.16 m

Explanation:

Given

initial temperature $=20^{\circ}C$

Final Temperature $=80^{\circ}C$

mass flow rate of cold fluid $\dot{m_c}=1.2 kg/s$

Initial Geothermal water temperature $T_h_i=160^{\circ}C$

Let final Temperature be T

mass flow rate of geothermal water $\dot{m_h}=2 kg/s$

diameter of inner wall $d_i=1.5 cm$

$U_{overall}=640 W/m^2K$

specific heat of water $c=4.18 kJ/kg-K$

balancing energy

Heat lost by hot fluid=heat gained by cold Fluid

$\dot{m_c}c(T_h_i-T_h_e)= \dot{m_h}c(80-20)$

$2\times (160-T)=1.2\times (80-20)$

$160-T=36$

$T=124^{\circ}C$

As heat exchanger is counter flow therefore

$\Delta T_1=160-80=80^{\circ}C$

$\Delta T_2=124-20=104^{\circ}C$

$LMTD=\frac{\Delta T_1-\Delta T_2}{\ln (\frac{\Delta T_1}{\Delta T_2})}$

$LMTD=\frac{80-104}{\ln \frac{80}{104}}$

$LMTD=91.49^{\circ}C$

heat lost or gain by Fluid is equal to heat transfer in the heat exchanger

$\dot{m_c}c(80-20)=U\cdot A\cdot$ (LMTD)

$A=\frac{1.2\times 4.184\times 1000\times 60}{640\times 91.49}=5.144 m^2$

$A=\pi DL=5.144$

$L=\frac{5.144}{\pi \times 0.015}$

$L=109.16 m$

6 0

3 years ago

A person is filling a knee-high bucket with water using a garden hose and holding it such that water discharges from the hose at

Serggg [28]

Answer:

Yes i am agree with this suggestion

Explanation:

Given that we have to assume that there is no any frictional affects.

As we know that when height increases then the discharge level will decreases when discharge level decreases then the time of filling for the bucket will increase.So the bucket will fill faster if the hose lowered until knee level.

Yes i am agree with this suggestion

8 0

3 years ago

A volleyball is dropped from a cliff and a soccer ball is thrown upward from the same position. When each ball reaches the groun

vredina [299]

The question is whether the statement is true or false.

The answer if false.

Explanation:

It is exactly the opposite. The soccer ball will hit the ground with greater velocity.

Since the soccer ball is thrown upward, when it returns to the same heigth from which it was throwm it will have a velocity downward, which will make that the soocer ball reaches the ground at the bottom of the clif with greater velocity than the volleball.

The greater the velocity with which the soccer ball is thrown upward, the greater its velocity when reaches the same point from which it was thrown, and the greater the velocity with which it will hit the ground at the bottom of the clif.

6 0

3 years ago

Design an experiment to test the rate at which temperature changes for two different masses (amounts) of water.

mrs_skeptik [129]

Answer:Experimental Question: How does the amount of a substance affect the rate at which temperature changes?

It depends on the conductivity of the material. If the shift is extreme, the temperature near the heating / cooling source will be similar to the temperature of the heating / cooling source and it will take time for the remainder of the material to rise to temperature. It will depend on the conductivity of the material.

Hypothes is:

Materials List:

• digital stopwatch

• 250ml beaker

• rubber bung

• thermometer

• bunsen burner

• tripod

• gauze

• retort stand and clamp

• goggles

Safety Procedures *:

1. Adult supervision is required.

2. Wear safety goggles, apron, and closed-toe shoes.

3. Do not wear baggy sleeves or dangling jewelry. Tie long hair back.

4. Use hot pads or oven mitts to handle hot objects.

5. Do not reach over a hot burner.

6. Do not leave the experiment unattended.

7. Clean up spills immediately.

8. Report any injuries to your Learning Coach or adult supervisor immediately

Experimental Procedures :

• Fill an empty beaker with exactly 150ml of water (check side-scale of beaker)

• Set up apparatus as shown above. Ensure the thermometer is about 2cm above the bottom of the beaker.

• Light the bunsen burner and put on a blue flame. Heat up the water.

• When the temperature on the thermometer has reached 90°C, immediately switch off the burner.

• Start the stopwatch and time for 5.0 minutes.

• Read the thermometer value at the 5.0 minute mark.

• Before repeating the experiment, check the level of water is still 150ml

Data Table:

Start Temperature of Water (°C) Temperature after 5min (°C) Drop in Temperature

(°C) Average Rate of Cooling x 1000 (°C/s)

80 70 10 17

75 66 9 15

70 62 8 13

65 59 6 10

60 55 5 8

Analysis:

Conclusions : There is a strong correlation between the average rate of cooling and the start temperature: the greater the start temperature, the faster the average rate of cooling.

Explanation:

use quillbot or this will be considered plagerism

3 0

3 years ago