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alex41 [277]
3 years ago
6

How many neutrons does element X have if its atomic number is 39 and its mass number is 79?

Physics
1 answer:
bazaltina [42]3 years ago
6 0

Number of neutrons: atomic mass - atomic number

Element X's atomic mass is 79 and its atomic number is 39. Subtract 39 from 79 to find how many neutrons Element X has.

79 - 39 = 40

Element X has 40 neutrons.

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A projectile is shot horizontally at 23.4 m/s from the roof of a building 55.0 m tall. What is the time necessary for the projec
baherus [9]
The horizontal speed has no effect on the answer. 

It doesn't matter whether you flick a marble horizontally from the roof,
fire a high-power rifle horizontally from the roof, drive a school bus straight
off the roof, or drop a bowling ball from the roof with zero horizontal speed. 
Their vertical speed is completely determined by gravity, (and it happens to
be the same for all of them).

Handy dandy formula for the distance covered by anything that starts out
with zero speed and accelerates to the end:

            Distance = (1/2) (acceleration) x (time)²

If the beginning of the journey is on Earth, then the acceleration is
9.8 m/s² ... the acceleration of gravity on Earth.  We'll assume that
the 55-meter rooftop in the question is part of a building on Earth.

                       55 meters  =  (1/2) (9.8 m/s²) x (time)²           

Divide each side
by  4.9 m/s² :            55 m / 4.9 m/s²  =  (time)²

                                 (time)²  =  (55/4.9)  sec²

Square-root
each side:                time  =  √(55/4.9 sec²)

                                           =      3.35 sec  .
5 0
3 years ago
THIS IS SCIENCE .What is most likely to happen during weathering? Moving of sediment Breaking down of rocks Laying down of sedim
MaRussiya [10]

The answer is B. Breaking down of rocks.

7 0
3 years ago
Consider the possible scenarios and determine which of them are true for positive feedbacks or negative feedbacks.A. Increased p
avanturin [10]

Answer:

Scenario A, B and E is True.

Explanation:

Scenario A) True. Removing carbon dioxide from atmosphere decreases greenhouse effect of atmosphere. Thus, temperature rise decreases.

Scenario B) True. The more evaporation creates the more greenhouse effect. Therefore, temperature rise increases.

Scenario C) False. Removing carbon dioxide from atmosphere decreases greenhouse effect of atmosphere. Thus, temperature rise decreases.

Scenario D) False. The more evaporation creates the more greenhouse effect. Therefore, temperature rise increases.

Scenario E) True. If reflected radiation increases from Earth, temperature rise of the Earth will decrease. Ice cover increases reflectivity which leads temperature level decrease.

Scenario F) False. If reflected radiation increases from Earth, temperature rise of the Earth will decrease. Ice cover increases reflectivity which leads temperature level decrease.

5 0
3 years ago
Type the correct answer in the box. use numerals instead of words. anne has a sample of a substance. its volume is 20 cm3, and i
CaHeK987 [17]

The density of sample is 5 g/cm3

Given:

volume of sample = 20 cm3

mass of sample = 100 grams

To Find:

density of sample

Solution: Density is the measure of how much “stuff” is in a given amount of space. For example, a block of the heavier element lead (Pb) will be denser than the softer, lighter element gold (Au). A block of Styrofoam is less dense than a brick. It is defined as mass per unit volume

density = mass/volume

d = 100/20

d = 5 g/cm3

So, density of sample is 5 g/cm3

Learn more about Density here:

brainly.com/question/1354972

#SPJ4

6 0
1 year ago
The orbital radius of an electron in a hydrogen atom is 0.846 nm. What is its de Broglie wavelength?
kotykmax [81]

Answer:

The  value  is  \lambda   = 1.329 *10^{-9} \  m

Explanation:

From the question we are told that

  The  orbital radius is  r =  0.846nm =  0.846 *10^{-9} \ m

Generally the de Broglie wavelength is mathematically represented as

      \lambda  =  \frac{2 *  \pi  r}{4}

substituting values

     \lambda  =  \frac{ 2 * 3.142  *  0.846 *10^{-9}}{4}

    \lambda   = 1.329 *10^{-9} \  m

6 0
3 years ago
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