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3 years ago

Why Is it important to have a control group in an experimental investigation

1 answer:

4 0

It is important to have a control group in an experimental investigation because if the experiment did not have the control group the data collected would not be accurate. For example if you're testing water turning into ice but you use a different freezer or ice tray for each experiment then there are some elements that would make your data inaccurate.

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The most common purpose for fracking in the u.s is to get

sveta [45]

Natural gas is the answer.

5 0

4 years ago

2. Air at a temperature of 20 ºC passes through a pipe with a constant velocity of 40 m/s. The pipe goes through a heat exchange

frozen [14]

Answer:

a) Q = 1436 kW

b) P ≈ 776 kW

Explanation:

Let's begin by listing out the given parameters:

T1 = 20 °C, u = 40 m/s, T2 = 820 °C, P = 4.3 kW, m = 2.5 kg/s, T3 = 510 °C, V1 = 40 m/s,

V2 = 40 m/s, V3 = 55 m/s, ṁ = 2.5 kg/s

To solve the question, we make this assumption that the size of the pipe is constant

a) No change in velocity implies that heat added is isochoric

Q = m * C * ΔT

Cv of air at 300 K(≈20 °C) = 0.718

Q = 2.5 * 0.718 * (820 − 20)

Q = 1436 kW

b) P = ṁ * Cp * ΔT + ṁ * (V2² - V3²) ÷ 2000] - Ql

V2² - V3² = 55² - 40² = 1425

ΔT = T2 - T3 = 820 - 510 = 310 °C

Cp of air at 300 K(≠20 °C) = 1.005 kJ/kgK

Ql = 4.3 kW

P = 2.5 * (1.005 * 310) + 2.5 * (1425 ÷ 2000) - 4.3

P = 778.875 + 1.78125 - 4.3 = 776.35625

P ≈ 776 kW

7 0

4 years ago

Which formula describes acceleration? m/s^2 m/s s/m m2

Aleks04 [339]

Answer:

m/s^2

Explanation:

Force = mass × acceleration

kgm/s^2 = kg × acceleration

where acceleration = Force ÷ mass

= kg m/s^2 ÷ kg

:Acceleration = m/s^2

3 0

4 years ago

A light-rail commuter train accelerates at a rate of 1.35 m/s2. How long does it take to reach its top speed of 80.0 km/h, start

Alona [7]

Answer:

16.46 seconds.

13.46 seconds

2.67 m/s²

Explanation:

Acceleration = a = 1.35 m/s²

Final velocity = v = 80 km/h = $80\frac{1000}{3600}=\frac{200}{9}\ m/s$

Initial velocity = u = 0

Equation of motion

$v=u+at\\\Rightarrow \frac{200}{9}=0+1.35t\\\Rightarrow t=\frac{\frac{200}{9}}{1.35}=16.46\ s$

Time taken to accelerate to top speed is 16.46 seconds.

Acceleration = a = -1.65 m/s²

Initial velocity = u = 80 km/h= $80\frac{1000}{3600}=\frac{200}{9}\ m/s$

Final velocity = v = 0

$v=u+at\\\Rightarrow 0=\frac{200}{9}-1.65t\\\Rightarrow t=\frac{\frac{200}{9}}{1.65}=13.46\ s$

Time taken to stop the train from top speed is 13.46 seconds

Initial velocity = u = 80 km/h= $80\frac{1000}{3600}=\frac{200}{9}\ m/s$

Time taken = t = 8.3 s

Final velocity = v = 0

$v=u+at\\\Rightarrow 0=\frac{200}{9}+a8.3\\\Rightarrow a=\frac{-\frac{200}{9}}{8.3}=-2.67\ m/s^2$

Emergency deceleration is 2.67 m/s²

3 0

3 years ago

What is the deferent between expansion and contraction

expeople1 [14]

The increasing in size of an object on heating is called expansion where the decrease in size of an object on cooling is calles contraction.

8 0

3 years ago