A) -0.5(9.8)*t^2 = -25(t-2) - 0.5(9.8)(t-2)^2
-4.9t^2 = -25t + 50 - 4.9(t^2-4t+4)
0 = -25t+50+19.6t - 19.6
5.4t = 30.4
t = 5.62962963 s

b) h = -4.9(5.62962963)^2
h = -155.2943759
the building is 155.2943759 m high

c) speed 0of first stone
= at
= 9.8*5.62962963
= 55.17037037 m/s
speed of second stone
= v + at
= 25+9.8*3.62962963
= 60.57037037 m/s

7 0

3 years ago

An atom has atomic number of 34. how many protons and electrons does it have? what is its symbol? 34 protons and electrons. se l

AURORKA [14]

Se: Selenium

Protons: 34
Electrons: All atoms in the periodic table are neutral until changed otherwise
Neutrons: 44
Atomic Mass: 78.09

>Symbol attached<

4 0

3 years ago

. A bright violet line occurs at 435.8 nm in the emission spectrum of mercury vapor. What amount of energy, in joules, must be r

Tom [10]

Answer : The energy released by an electron in a mercury atom to produce a photon of this light must be, $4.56\times 10^{-19}J$

Explanation : Given,

Wavelength = $435.8nm=435.8\times 10^{-9}m$

conversion used : $1nm=10^{-9}m$

Formula used :

$E=h\times \nu$

As, $\nu=\frac{c}{\lambda}$

So, $E=h\times \frac{c}{\lambda}$

where,

$\nu$ = frequency

h = Planck's constant = $6.626\times 10^{-34}Js$

$\lambda$ = wavelength = $435.8\times 10^{-9}m$

c = speed of light = $3\times 10^8m/s$

Now put all the given values in the above formula, we get:

$E=(6.626\times 10^{-34}Js)\times \frac{(3\times 10^{8}m/s)}{(435.8\times 10^{-9}m)}$

$E=4.56\times 10^{-19}J$

Therefore, the energy released by an electron in a mercury atom to produce a photon of this light must be, $4.56\times 10^{-19}J$

3 0

3 years ago

Identify the situation where work is being done. Carrying a box of crayons across the room. Lifting a backpack off the floor Hol

Likurg_2 [28]

Lifting the backpack off the floor. Force is being applied in only one direction then (up) which is what constitutes as work. Carrying the box of crayons applies force in two directions (up and forward), which cancel each other out. Work has a vector, which is a quantity containing both direction and magnitude (one, finite direction, not two).

7 0

3 years ago

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