and closing
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The heart has 4 valves. They are what makes the lub-dub lub-dub sounds that can be heard from the chest.
The mitral valve is located between the left atrium and the left ventricle. It closes the left atrium to collect oxygenated blood from the lungs and opens to pass it on to the left ventricle.
The tricuspid valve is located between the right atrium and the right ventricle. It closes the right atrium to hold unoxygenated blood and opens to pass it on to the right ventricle ensuring a one way flow.
The aortic valve is located between the aorta and the left ventricle. It closes the left ventricle and opens to the aorta to pass on the oxygen-rich blood to the body.
The pulmonary valve is located between the pulmonary artery and the right ventricle. It closes off the right ventricle and opens to pass on unoxygenated blood to the lungs.
A 5kg backpack will weigh 49 newtons on earth
Don't over think it!
For example, if you do 5 laps in 5 minutes then you do one lap per minute. If you use that example and you apply it to your problem you'll notice that the answer is simply C. 1km/min.
Best wishes!
PHysical properties are properties that do not involve changes in the molecular level. In this case, malleability and magnetism are physical.
Chemical properties involve changes to the substance at the molecular level or change its identity. In this case, reacting with oxygen and nonflammability is a chemical property.
When one object is rubbed against another, static electricity can be created. This is because the rubbing creates a negative charge that is carried by electrons.
