Answer:
50.67
Explanation:
L = 4 m
Let the mass of small length dx is dm.
So, dm = ρ(x) dx
Integrate on both the sides within proper limits
![m = \left [ 10x+\frac{4}{3}x^{\frac{3}{2}} \right ]_{0}^{4}](https://tex.z-dn.net/?f=m%20%3D%20%5Cleft%20%5B%2010x%2B%5Cfrac%7B4%7D%7B3%7Dx%5E%7B%5Cfrac%7B3%7D%7B2%7D%7D%20%5Cright%20%5D_%7B0%7D%5E%7B4%7D)
m = 40 + 32 / 3 = 152 / 3 = 50.67
True: the time of flight of the two balls is the same
Explanation:
The ball that is dropped is in free fall, so its time of flight can be determined by using the suvat equation
where
is the vertical displacement, which is the height from which it was dropped
u = 0 is the initial vertical velocity
is the acceleration of gravity
t is the time of flight
Solving for t,
The ball thrown horizontally follows a projectile motion, which consists of two independent motions:
- A uniform motion (constant velocity) along the horizontal direction
- A uniformly accelerated motion, with constant acceleration (acceleration of gravity) in the downward direction
However, the time of flight is completely determined by the vertical motion only, therefore using the equation:
where u = 0 is the initial vertical velocity of the ball (which is zero, since it is thrown horizontally). Since the ball is thrown from the same height, its time of flight is still
So, the two balls reach the grund at the same time.
Learn more about free fall and projectile motion:
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#LearnwithBrainly
Mercury looks pretty, in its shiny, fast-moving liquid form, but don't touch! It can be extremely poisonous to humans.
The symbol Hg that mercury is known by comes from its Greek name, hydrargyrum, which means "liquid silver" — to reflect its shiny surface. The element is also known as quicksilver for its mobility. Named after the fastest-moving planet in the solar system, mercury has been known to humanity for ages. In fact, evidence of its use has been found in China, India and Egypt, and traces of mercury were found in 3,500-year-old Egyptian tombs.
Mercury is a very toxic element. It can enter the body through an open wound or by inhaling or ingesting it. It can then cause damage to nerves, the liver and the kidney, as well as a number of other symptoms.
Despite its toxic qualities, mercury can still be useful to us. The element conducts electricity and is used in electrical switches of thermostats and certain types of doze alarm-type alarm clocks, according to the College of Natural Resources at the University of California, Berkeley (CNR) "The place where people probably see it most commonly is in the new light bulbs — the compact fluorescent light bulbs," where mercury vapor is one of the chemicals used, said Daniel King, an associate professor of chemistry at Drexel University.
Due to its high density and compactness, mercury is also used to make thermometers, barometers and other scientific instruments, according to the Jefferson Lab. However, for safety reasons, consumer use of mercury in thermometers has become less common over the years, as digital thermometers have been introduced. In 2008, 13 states introduced laws that limit the manufacture, sale and/or distribution of mercury fever thermometers: California, Connecticut, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Hampshire, Rhode Island, Oregon, Washington, the Environmental Protection Agency reports.
Just the facts
Atomic number (number of protons in the nucleus): 80
Atomic symbol (on the Periodic Table of Elements): Hg
Atomic weight (average mass of the atom): 200.59
Density: 13.5336 grams per cubic centimeter
Phase at room temperature: Liquid
Melting point: minus 37.8 degrees Fahrenheit (minus 38.83 degrees Celsius)
Boiling point: 674.11 F (356.73 C)
Number of isotopes (atoms of the same element with a different number of neutrons): 34. Number of stable isotopes: 7
Most common isotope: 202Hg (29.9 percent natural abundance)
Mercury is typically found in the form of its common ore cinnabar — mercury sulfite — and can rarely be found on its own. To extract pure mercury, the ore is ground up and heated to the temperature of about 1,076 degrees F (580 degrees Celsius) with oxygen present in the process. Mercury vapor escapes from the ores and sulfur dioxide is removed, according to CNR. The metal is condensed and washed with nitric acid to purify it, and then distilled.
Mercury can form alloys with gold, silver, zinc and cadmium, which are called amalgams. Through those amalgams, mercury can be used to extract gold from rocks. When mercury comes into contact with gold, the gold dissolves into the mercury and then the two are separated, with the mercury being distilled off.
Mercury also forms compounds with other elements. Interestingly, one of such compounds — mercury nitrate — played a role in the coining of the term "mad as a hatter."
"Mercury was actually used in the making of hats from animal pelts," King said. In the 18th century people used the mercury nitrate compound to clean the pelts before they turned them into hats.
"And they discovered that a large percentage of the people who were working with those chemicals ended up suffering from brain damage," he said. "So the term 'mad as a hatter' actually comes from exposure to mercury."
Answer:
48%
Explanation:
The earth's temperature has to be stable and this is the reason for the presence of incoming and outgoing heat. Of the solar energy reaching the atmosphere, about 29% is bounced back as reflected radiation by clouds, snow and particles in the atmosphere, about 23% is absorbed by the atmosphere and about 48% actually gets to the earth surface.
Answer:
Wear a helmet. Stay visible; use bike lights and/or wear bright clothes. Look and Signal; use hand signals to let drivers know where you're going, try to make eye contact with them and look before you go.
Explanation:
