Answer:
fr = 269.3 N
Explanation:
Let's use Newton's second law, for this it is good to see the attached diagram,
X axis
fr -F2 = 0
fr = F2
Y Axis
N-W = 0
We must include the rotation balance, place the rotation point at the bottom of the ladder and take the positive counterclockwise turns.
Σ τ = 0
F2 x -W y / 2 = 0
We look for x and y with trigonometry
sin 70 = y / L
cos 70 = x / L
y = L sin70
x = L cos 70
We substitute and calculate F2
F2 L cos 70 = W L sin 70 / 2
F2 = mg/2 tan 70
F2 = 20 9.8/2 tan 70
F2 = 269.3 N
From the first equation (x axis)
fr = F2
fr = 269.3 N
In a spectrograph, black lines can be seen going through the array of colors. The pattern of these lines indicate the composition of the star.
Different elements block different parts of the spectrum, resulting in black lines.
On the periodic table, the element “K’ represents Potassium. Potassium has an atomic number of 19. It has an atomic mass of 39.098. The number of protons is equal to the atomic number, so Potassium has 19 protons. To find the number of neutrons in an element, subtract the atomic mass from the atomic number. (39-19). This means that the element K has 20 neutrons. Finally, to find the number of electrons, you just take the atomic number, and you have your number of electrons. Thus, Potassium has 19 electrons.
The tricks above work for any element on the Periodic Table, so feel free to use them! Here is a little way to remen then by:
A = P = E M - A = N
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T R L M T E
O O E A O U
M T C S M T
I O T S I R
C N R C O
S O N
# N # S
S
I really hope this helps :)
<span>x = 129.9 m
y = 30.9 m
First, let's calculate the horizontal and vertical velocities involved
h = 50.0cos(30) = 43.30127 m/s
v = 50.0sin(30) = 25 m/s
The horizontal distance is simply the horizontal velocity multiplied by the time, so
43.30127 m/s * 3 s = 129.9 m
So the horizontal distance traveled is 129.9 m, so x = 129.9 m
The vertical distance needs to take into account gravity which provides an acceleration of -9.8 m/s^2, so we get
d = 25 m/s * 3s - 0.5*9.8 m/s^2 * (3 s)^2
d = 75 m - 4.9 m/s^2 * 9 s^2
d = 75 m - 44.1 m
d = 30.9 m
So the vertical distance traveled is 30.9 m, so y = 30.9 m</span>
We can solve the problem by using the law of conservation of energy.
Initially, the rock has only gravitational potential energy, which is given by
where mg is the weigth of the rock (2200 N), while h is the height at which the rock has been released (h=15 m). If we calculate it, we get
Just before hitting the ground, the rock height is zero, so its potential energy is now zero. So the total mechanical energy of the rock now is just kinetic energy:
however, the mechanical energy of the rock must be conserved, so
and so we have that the kinetic energy of the rock just before hitting the ground is equal to its initial potential energy: