Key concepts
Heart rate
Exercising
The heart
Cardiovascular system
Health
Introduction
As Valentine's Day approaches, we're increasingly confronted with "artistic" images of the heart. Real hearts hardly resemble to two-lobed shapes adorning cards and candy boxes this time of year. And the actual shape of the human heart is important for its function of supplying blood to the entire body. You have likely noticed that your heart beats more quickly when you exercise. But have you ever taken the time to observe how long it takes to return to its normal rate after you're done exercising? In this science activity you'll get to do some exercises to explore your own heart-rate recovery time.
Background
Your heart is continuously beating to keep blood circulating throughout your body. Its rate changes depending on your activity level; it is lower while you are asleep and at rest and higher while you exercise—to supply your muscles with enough freshly oxygenated blood to keep the functioning at a high level. Because your heart is also a muscle, exercise, in turn, helps keep it healthy. The American Heart Association recommends that a person does exercise that is vigorous enough to raise their heart rate to their target heart-rate zone—50 percent to 85 percent of their maximum heart rate, which is 220 beats per minute (bpm) minus their age for adults—for at least 30 minutes on most days, or about 150 minutes a week in total. So for a 20-year-old, the maximum heart rate would be 200 bpm, with a target heart-rate zone of 100 to 170 bpm. (For those 19 or younger, target zones can vary more than they do for adults.)
i think it will help you...if it help you ...please mark brainless
"Apparent magnitude" means how bright a star looks to
a person on Earth.
-- The star that appears brightest is the one with the
lowest-number apparent magnitude . . . Star-C, at -4 .
-- All of them are visible from Earth, but may require some 'help'.
The dimmest stars visible with good human eyes under dark,
non-polluted skies are those with apparent magnitude around 6.
Stars B and C would be visible to the unaided eye, but Star-A
would require binoculars.
Around here, a few miles outside of the Chicago city limits, we're
lucky to see Magnitude-4 without binoculars.
-- It's not possible to determine which star has the highest luminosity.
The apparent magnitude depends on the star's distance from Earth
as well as its luminosity.
A flashlight 3 feet from your face appears much brighter than any
star, although any star is more luminous than the flashlight.
Distance from you has a lot to do with it.
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"Absolute magnitude" means how bright each star would appear
to a person on Earth if all stars were at the same distance from us.
(The distance happens to be 32.6 light years.) It only depends on
the star's real luminosity, not on its distance.
-- It's not possible to determine which star appears brightest.
Star-C (absolute -7) would appear brightest if all stars were
equal distances from us. But a flashlight ... which has a huge-
number absolute magnitude because we couldn't see at all from
32.6 light years away ... can appear very bright from 3 feet in
front of your face.
-- They're all visible from Earth, but a star with absolute magnitude
greater than 6 would need binoculars (or better) to be visible.
-- Yes, if you know a star's absolute magnitude, then you know its
luminosity. The lowest-number absolute magnitudes are the ones
that would appear brightest if all stars were the same distance from
us, so they're the stars with the greatest luminosity. From this group,
that's Star-C.
Answer:
The answer is B. When the magnet is placed on a globe to correctly align with Earth’s magnetic field, it is considered to be suspended freely. The Earth has geographical poles as well with North and South poles. Since unlike poles attract, the South Pole of the magnet will be attracted to the geographical North.
Explanation: