Để có 100 lít nước ở 370C. Người ta pha nước đang sôi với nước ở 150C. Tính thể tích nước mỗi loại cần dùng.Biết khối lượng riêng của nước là 1000kg/m3
Answer:
nước sôi: 440/17 l
nước 15°C:1260/17 l
Indoor pollution experts conducted an analysis of the paint used in many office buildings which revealed that the paint contains traces of lead. The lead seems to rise to the surface of the paint and escape into the building's air supply. Tests show that because of the chemical drying process, the lead is not discernible on the surface until the paint has been on the walls for at least six months. To meet safety standards, owners should repaint walls at least every six months, or cover the walls with a different material.Which of the following, if true, would most weaken the conclusion above?A) The indoor pollution experts had no clear understanding of why it took six months for the lead to become discernible on the paint's surface.B) The indoor pollution experts neglected to examine the paint for traces of other toxic substances such as cadmium and mercury.C) The amount of lead found on the surface of the paint after six months remained constant for the next two years.D) The indoor pollution experts found that even in those offices painted with a different brand of paint, traces of lead were still found in the air workers breathed.E) The indoor pollution experts' research shows that the amounts of lead that come into contact with the air people breathe, even in the office buildings that used the greatest amount of paint, are too low to affect workers.
Answer:
E) The indoor pollution experts' research shows that the amounts of lead that come into contact with the air people breathe, even in the office buildings that used the greatest amount of paint, are too low to affect workers
Explanation:
The conclusion that would weaken the above statement if true was that the amount of lead found in air was not hazardous for the people living in building and the effects of such paint was quite low o affect workers.How can you say gravitational force is a field force
Answer:
because gravity pulled us in the land if there is no gravitational force there will not be field force too
Explanation:
hope it's will help you
Answer the following questions 1 What is the difference between mass and weight of an object. Will the mass and weight of an object on the earth be same as their values on Mars ? Why?
Answer:
difference between mass and weight is that mass is amount of matter in a material while weight is a measure of how the force of gravity acts upon that mass.the mass of an object will be same on earth and mars but its weight on both planets will be different.
A group of students are designing a field study to investigate the length of time a traffic light remains yellow.
Answer:
3 to 7 seconds.
Explanation:
According to the traffic engineers the length or the duration of the signal to turn form yellow or amber to green is more than 5 seconds. A time interval is needed to easy out the traffic flow.Highlight 2 factors which shows that heat from the sun does reach the earth surface by convection
Define measurement with 10 points
Answer:
the process of comparing unknown quantities with known standards quantities are known as measurement
express in standard form
(I)0.000038
Answer:
3.8 x 10^-5
Explanation:
all you doing is putting it in the standard form I hope this help
which two phenomena make up electromagnetism?
A) moving charges in an electric current attract each other
B) permanent magnets form a magnetic field from one pole to the other pole
C) an electric current causes a magnetic field around a core of magnetic metal
D) a moving magnet causes an electric current in a magnetic metal
Explanation:
the correct answer is option ( C ) and ( D )
a teacher drives from school to the mall. then she goes to the doctors office for a physical examination. what is the magnitude of her displacement
The magnitude of the teachers displacement is the difference between
the location of the school and the location of the doctors office
The reason behind the above expression are explained as follows
The known locations of the teacher;
Initial location; The school
Second location; The mall
The eventual location; The doctors office
The required information;
The magnitude of the teachers displacement
The method of obtaining the displacement of the teacher;
Qualitatively, the displacement of the teacher can be obtained by applying the definition of displacement as follows;
The definition of displacement is an object's change in position, given by the difference between its start and finish locations
According to the definition of displacement, therefore, the magnitude of
the teachers displacement is the distance between the school and the
doctors office which is given by the difference between the coordinates of
the location of the school and the location of the doctors office
The magnitude of the displacement of the teacher = The coordinate of the location of the doctors office - The coordinate of the location of the school
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Luis rushes 40m toward his truck. He notices he forgot his shoes and returns back to his house. His total travel time is 60s.
What is Luis’s average speed over the 60s?
What is Luis average velocity over the 60s?
1. The average speed of Luis over the 60 s is 1.33 m/s
2. The average velocity of Luis over the 60 s is zero.
1. The average speed can be calculated with the following equation:
[tex] S = \frac{d}{t} [/tex]
Where:
d: is the total distance traveled
t: is the total time = 60 s
The total distance can be calculated by the sum of the distance traveled to the truck (40 m) and the distance traveled to his home (the same 40 m), as follows:
[tex] d = 40 m + 40 m = 80 m [/tex]
So, the average speed is:
[tex] S = \frac{d}{t} = \frac{80 m}{60 s} = 1.33 m/s [/tex]
Hence, Luis's average speed over the 60 s is 1.33 m/s.
2. Now, the average velocity is a vector given by:
[tex]v = \frac{\Delta x}{\Delta t} = \frac{x_{f} - x_{i}}{t}[/tex]
Where:
[tex]x_{f}[/tex]: is the final distance traveled (the way to his home) = 40 m
[tex]x_{i}[/tex]: is the initial distance traveled (the way to his truck) = 40 m
Δt: is the total time = t = 60 s
Given that Luis in his journey, returns to the same starting point (his house), the total displacement is zero, and so the average velocity is also zero:
[tex]v = \frac{x_{f} - x_{i}}{t} = \frac{40 m - 40 m}{60 s} = 0[/tex]
Therefore, Luis's average velocity over the 60 s is zero.
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As shown in the figure below, Luis rushes 40 m toward his truck. He notices he forgot his shoes and returns back to his house. His total travel time is 60 s.
Answer:
What is Luis’s average velocity over the 60 s period?
Answer: 0 m/s
What is Luis’s average speed over the 60 s period?
Answer: 1.33 m/s
thin wires have high resistance whereas thick wires have low resistance why???
can anyone say answer of this ^_^
Answer:
The resistance of a thin wire is greater than the resistance of a thick wire because a thin wire has fewer electrons to carry the current. The relationship between resistance and the area of the cross section of a wire is inversely proportional .
The best way to think about this is:
A thick/wide road, with many lanes, can carry more cars than a thin/narrow road, with only one or two lanes.
A city bus travels along its route from Jackson Street 8 km to Aurora Avenue, where it turns and continues 13 km.
What is the total distance that the bus has traveled? km
The total displacement of the bus is approximately 15 km northeast northwest southeast southwest.
im a bit confused on what the question is:(
if its just asking for the total number of km traveled it would be 21 km
A 4000 N force acts on an object that initially has a momentum of 400 kg-m/s for 0.9 seconds. What is the final momentum of the system?
Answer:
4360 Kgm/s
Explanation:
Applying,
Ft = M-M'................. Equation 1
Where F = force, t = time, M = Final momentum, M' = Initial momentum.
make M the subject of the equation
M = Ft+M'............ Equation 2
From the question,
Given: F = 4000 N, t = 0.9 seconds, M' = 400 kg-m/s
Substitute these values into equation 2
M = 4000+(0.9×400)
M = 4000+360
M = 4360 kgm/s
Hence the final momentum is 4360 kgm/s
whats the beginning of life called
Answer:
Abiogenesis in evolutionary science, not sure about creation science
Explanation:
Ploughing field with harrow pulled by a tractor is a modern technology
Ploughing field with harrow pulled by a tractor being a modern technology is true.
What is Technology?This involves the use of scientific knowledge to tackle different life problems and has different sectors.
Ploughing field with harrow pulled by a tractor involves machines and not manual labour which makes it a modern technology.
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Why does a ship float on water when it weighs about 100tones and why a stone of less than a kg sinks
Answer with Explanation:
Let me answer this in a simple way, since the density of stone is greater than that of water, the stone sinks as the weight of the stone is greater than the weight of water displaced by it. But the ship is designed in such a way that the relative density of the ship always becomes less than that of water. Therefore, the weight of the water displaced becomes equal to the total weight of the ship and thus it floats.
There are many other ways to explain this but this should give you the general idea.
what is required for force to come into play
Answer:
An interaction of one object with another object results in a force between the two objects. Thus, at-least two objects must interact for a force to come into play.
state the advantages and disadvantages of alkaline battery over a lead acid accumulator
Answer:
Alkaline batteries have longer shelf life than other batteries of the chloride type electrolyte batteries. They have a much higher energy density compared with other batteries. This allows the battery to produce the same energy while lasting longer than other batteries.
Advantage
1) Alkaline battery lasts long than other batteries
2) It have a much higher energy density
Disadvantage :
1) They are heavier and bulkier
2) They have high internal resistance
What is alkaline battery ?An alkaline battery is a type of primary battery that derives its energy from the reaction between zinc metal and manganese dioxide.
Advantage
Alkaline battery can produce same amount of energy by lasting longer than other batteries as it have longer shelf life than lead acid accumulator
Alkaline battery have a much higher energy density compared to lead acid accumulator
Disadvantage :
Alkaline battery are heavier and bulkier
Alkaline battery have high internal resistance
learn more about Alkaline battery
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"Measurement is essential in our life. Justify the statement.
Explanation:
Measurement plays an important role in our daily lives because they are useful to do basic tasks, such as taking the temperature of a child with the help of a thermometer,making time estimations,measure out medicines and find out weights, areas and volumes of different substances
Difference between gravitational force and frictional
Explanation:
gravitational force or gravity is the force of attraction between objects that have mass.
frictional force is the forec that opposes motion (movement) when two surface are in contact. (acts in the opposite direction of motion)
so to sum it up,
- gravtional force is the force of attraction between objects that have mass.
- objects on the earth have weight because of gravitational force between them and the earth.
frictional force
- oppose motion
- slow down and stop moving objects and;
- produce heat
hope it helps :)
3. True or False: A warm-up can include minimal stretching at the end.
Answer:
False.
Explanation:
A warm up is stretching in the beginning.
Hess's law states that:
A. Energy cannot be created nor destroyed, it can only change form.
B. The enthalpy change when 1 mole of a substance undergoes complete combustion under standard conditions is equal to molar masses of the compounds.
C. When the enthalpy changes under standard conditions, 1 mole of a substance is formed from its elements.
D. The overall enthalpy change for a reaction is independent of the route the reaction takes.
Answer:
D. The overall enthalpy change for a reaction is independent of the route the reaction takes.
Answer: Hess's law states that the overall enthalpy change for a reaction is independent of the route the reaction takes. Option D is correct.
It is given Hess's law.
It is required to state the Hess's law.
What is Hess's law ?Thermochemical equations can be manipulated to give the data chemical reactions. We find exactly how much energy will be absorbed or released by the reaction because we may face various explosions.
There are mainly two ways to calculate ΔH of any reaction. First If the reaction has ΔH then the reverse of the reaction will have opposite ΔH and the second is if double the ΔH of the substances, double the ΔH.
Therefore Hess's law states that the overall enthalpy change for a reaction is independent of the route the reaction takes.
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a sphere of diameter 6.0
cm is moulded into a thin wire of diameter 0.2 mm calculate the length of the wire in metres
Answer:
V1 = 4/3 pi R^3 = pi D^3 / 6 D = 2 R volume of sphere
V2 = pi r^2 L = pi d^2 L / 4 volume of wire
V2 / V1 = 1 = 3/2 d^2 L / D^3 since volumes are equal
L = 2/3 D^3 / d^2 = 2/3 * 6^3 / .02^2 = 360,00 cm = 3600 m
why does apparent depth of different liquids vary
the slope of a line on a position vs time graph is the
a. velocity
b. time
c. distance
d. displacement
It's the velocity, but only the magnitude. It can't show the direction of the velocity. So it's better to call it speed.
The fluid inside the hydraulic jack has a pressure of 30,000 Pa. If the surface of
the piston that is used to lift an object is 0.1 m’in area, how much weight can
the jack lift?
Explanation:
p = F /A
F = P×A
F = 30,000 Pa / 0.1 m²
F = 300,000 N
A force of 15N acts on an area of 60m².What is the pressure? *
Answer:
0.25p.a
Explanation:
force=15N area=60m²
so pressure =force/area =15N/60m²=0.25p.a
define electrical resistance in a metal conductor
Answer:
Resistance is defined as the property of a conductor to resist the flow of charges through it. The resistance of conductor is numerically given as the ratio of potential difference across its length to the current flowing through it.
Explanation:
Why does a small piece of steel rod sinks while a large steel oil tanker floats?
Plss help thanks! pls include EXPLANATION and EXAMPLES that I can proof to people that has no knowledge
Answer:
Too what i know its because of the air
Explanation:
The steel rod is more dense and doesnt have air whil'st the oil tanker is less dense with lots of air
