Science help please!

Answer:

15%

Explanation:

Step one:

Given data

Energy source= 300J

Useful energy = 45J

Waste energy = 255J

Required

The efficiency of the solar system

Step two:

The efficiency is computed by factoring only the useful work and the energy source

Efficiency= 45/300*100

Efficiency= 0.15*100

Efficiency= 15%

Answer:

Prolonged exposure to extreme heat can cause heat exhaustion, heat cramps, heat stroke, and death, as well as exacerbate preexisting chronic conditions, such as various respiratory, cerebral, and cardiovascular diseases.

Answer:

C. infrared waves

Explanation:

Microwaves are the electromagnetic waves which would the best to use in an object designed to cook food. Thus, the correct option is D.

Microwave is a form of electromagnetic radiation with the wavelengths ranging from about one meter to about one millimeter which is corresponding to the frequencies in the range between 300 MHz and 300 GHz, respectively.

Microwaves are used for cooking food faster than the conventional ovens and would not make a mess in the process. This reheats food instantly quickly. It is helpful for the health conscious people. Microwaves also ensure that a person will never burn the food again. Microwaves are also very economical and energy efficient.

Therefore, the correct option is D.

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Answer:

 μ = 0.49

Explanation:

For this exercise we can use Newton's second law

Y Axis

       N - W = 0

       N = W = mg

X axis

       -fr = ma

the equation for the friction force is

        fr = μ N

we substitute

       -μ  m g = ma

        μ = -a / g

we calculate

      μ = 4.8 / 9.8

      μ = 0.49

Answer:

Speed: Distance per time, 400 km/h, and a scalar quantity.

Velocity: Displacement per time, 20 m/s south, and a vector quantity.

Explanation:

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Answer:a goal is scored by throwing the ball into the goal post and is confirmed by deciding that’s if the ball has hit the tape mark or not

Explanation:

Answer: T = 40%

Explanation: The definition of Transmittance is a part of the incident light that passes through a surface or material moves through the other side of the surface. It is represented as T and is defined as the ratio of the intensity of incident light to the intensity of light that passes through the surface:

[tex]T=\frac{I}{I_{0}}[/tex]

where

I is intensity that passes through

I₀ is incident intensity

When you shine a light on a material and 50% of it is reflected, the remaining 50% will try to pass through. However, 10% is absorbed leaving 40% of the light to move through the other side of the surface.

So, Transmittance of this surface is 40%.

Answer:

vB' = 0.075[m/s]

Explanation:

We can solve this problem using the principle of linear momentum conservation, which tells us that momentum is preserved before and after the collision.

Now we have to come up with an equation that involves both bodies, before and after the collision. To the left of the equal sign are taken the bodies before the collision and to the right after the collision.

[tex](m_{A}*v_{A})+(m_{B}*v_{B})=(m_{A}*v_{A'})+(m_{B}*v_{B'})[/tex]

where:

mA = 0.355 [kg]

vA = 0.095 [m/s] before the collision

mB = 0.710 [kg]

vB = 0.045 [m/s] before the collision

vA' = 0.035 [m/s] after the collision

vB' [m/s] after the collison.

The signs in the equation remain positive since before and after the collision, both bodies continue to move in the same direction.

[tex](0.355*0.095)+(0.710*0.045)=(0.355*0.035)+(0.710*v_{B'})\\v_{B'}=0.075[m/s][/tex]

Answer:

P=I*I*R

Where P is power

I is current

R is Resistance

P=2*2*100

P=400W

Explanation:

Power is the rate of doing work.

From the Ohm’s law V=IR

Power=I*I*R

Answer:

1260ft

Explanation:

Given parameters:

Speed  = 105ft/s

Time  = 12s

Unknown:

Skidding distance of the truck  = ?

Solution:

To solve this problem:

       Distance  = speed x time

Now insert the parameters and solve;

  Distance  = 105 x 12  = 1260ft

Answer:

solids

Explanation:

beacause if you take an ice cube does it change its shape no and if it has a definite shape it is sure to have a definite volume

Answer: matter

Explanation:

The person with the greatest density will hit the earth first.

This is regarded as the mass per unit volume of a substance.

Density = mass/ volume

In objects with different densities, the drag and buoyancy forces will be the

same. They will however have different gravitational force in which the

denser object has more compared to lighter ones.

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Major land–use changes have occurred in the United States during the past 25 years. The total area of cropland, pastureland and rangeland decreased by 76 million acres in the lower 48 states from 1982 to 2003, while the total area of developed land increased by 36 million acres or 48%. What are the potential economic, social and environmental impacts of land use changes? How does land use change affect agriculture and rural communities? What are the important economic and environmental implications for commodity production and trade, water and soil conservation, open space preservation, and other policy issues? This article addresses some of these issues and their policy implications.

Answer:

TRUE

Explanation:

Answer:

Blood, semen, bodily fluids, breast milk

Explanation:

Explanation:

Through.....

1) blood

2) breast feeding

3) semen

4) unprotected sex etc

Answer:

Angle of Refraction ?

Explanation:

My decided answer on this question

Answer:

advantages of using renewable energy resource

it is safer and cleaner

it does not produces green house gas and has 0 carbon emission

for producing electricity we use solar and wind power that does not harm the environment

advantages of using non renewable energy resource

they are abundant

they are affordable

easy to use

they are easily accessible and compatible

easy to store

Answer:

as the ball is thrown, the enegry rises up, when it falls, the ball relseases all energy

Explanation:

Answer :

Label A - nucleus.

Label B- electron cloud.

Explanation :

An atom is the smallest unit of a matter that consist of three subatomic particles which are electrons, protons and neutrons.

The protons and the neutrons are located inside the nucleus or the center of the nucleus where the mass of the an atom is concentrated.

The electrons are located around the nucleus.

The protons are positively charged, the electrons are negatively charged and the neutrons are neutral that means it has no charge.

In the picture, label A shows the nucleus.

Electrons has the ability to revolve around the nucleus in a fixed circular orbit. Electron cloud represents the spreading of the electrons energy.

In the picture, label B shows the electron cloud.

Hence, the label A - nucleus and label B- electron cloud.

Answer:

C. HertzPrung Russel Diagram

Explanation:

The Hertzsprung–Russell diagram, or H–R diagram, is a plot of stellar luminosity against surface temperature. Most stars lie on the main sequence, which extends diagonally across the H–R diagram from high temperature and high luminosity to low temperature and low luminosity.

Answer:

The body becomes a positive charged body.

Explanation:

Given that two objects are shown below. One is neutral and the other is negative. What do you predict would happen?

According to the law of static electricity, like charges repel each other while unlike charges attract each other.

Since one of the object is neutral and the other one is negative, there will neither attraction nor repulsion between them.

Also, according to Electrostatic induction, the neural body can be charged and becomes positive.

The negative body will attract all the positive charges to its side, and repel all the negative charges to the other side. If the body is touched at the other end, the whole negative charges will be earthed and the body will become a positive body.

Answer:

its C

Explanation:

The statement that describes the relationship between the environment and the collective health of the world is; "what is good for the environment is good for our health."

Humans must maintain a very good interaction with their environment because the interaction between man and his environment is very necessary for healthy living.

Man depends on water, air etc to sustain life. These are part of the natural environment, when these are polluted due to neglect of the environment, human health is adversely affected.

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Hydrostatic pressure is the pressure exerted by an incompressible fluid (a liquid) at a given point, due to the weight of the fluid above it. Atmospheric pressure is the pressure exerted on a surface by the weight of the atmosphere (a compressible fluid) above it.

Answer:

29.4m/s

Explanation:

Given parameters:

Time  = 3s

Unknown:

Average velocity  = ?

Solution:

To solve this problem, we use the expression below:

      v  = u + gt

v is the average velocity

u is the initial velocity  = 0m/s

g is the acceleration due to gravity  = 9.8m/s²

t is the time

So;

        v  = 0 + (9.8 x 3)  = 29.4m/s

Answer:

hello your question is incomplete below is the missing part of the  complete question

which statement best describes Jean-Baptiste Fourier’s influence on Jean-François Champollion? Fourier shared his research about mathematics with Champollion, which aided him in his research. Fourier was the first to introduce Champollion to the hieroglyphs on the Rosetta Stone, which fascinated him. Fourier shared his findings about the Rosetta Stone with Champollion, which helped him in his research. Fourier was the first to introduce Champollion to a variety of languages, which prompted his love of languages.

answer :  Fourier was the first to introduce Champollion to a variety of languages, which prompted his love of languages.

Explanation:

Jean-Baptiste Fourier's influence on Jean-Francois Champollion is that Fourier was the first to introduce Champollion to a variety of languages, which prompted his love of languages. also Fourier was a mathematician  who pleaded on the behalf of Champollion when he was about to be adopted into the military.

Answer:

1. Schedule your activities

2. Prioritize the more important tasks

3. Avoid procrastination

Explanation:

Time-management techniques are strategies or methods developed by people to help them effectively manage their time. My best friend in the scenario above cannot effectively manage his time because he has a lot of activities crowding up his time.

To get better in his grades, he should strike a balance between school work and extracurricular activities. He should make a workable schedule where only the most important tasks are prioritized. He should also learn to execute these tasks on time without postponing them.

Answer:

Sample Response: He should decide on a study time that works best for him, create a study schedule, and manage his study sessions by using a daily to-do list

Explanation:

got it right on edge 2021

Answer:

positive. hope this helped