Answer:
54 km/hr
Explanation:
m/s to km/hr => 18/5
15 m/s to km/hr => 15 x 18/5 =>3 x 18 => 54km/hr
The mass number is the total number of protons and neutrons within an atom and since we know that the unknown element has 6 neutrons, we can simply subtract the number of neutrons from the mass number to get the number of protons.
17 - 6 = 11
There are 11 protons in this unknown element.
Extra:
The number of protons (+) and electrons (-) are equal in a neutral atom so since you know that there are 11 protons you also know that there are 11 electrons. On the periodic table, the element with 11 electrons is Na or Sodium.
Hope this helps! :)
The outer shell can hold 1 electron
Answer:
Energy needed = 54.02 J
Explanation:
the Energy in an elastic spring from hookes law is given as
F= ke , therefore the energy (E) is
E = 
K = 19.5 N/cm
e = 1.39cm
E = 
x 19.5 x 1.39
E = 13.55 J
The energy to stretch the spring for 6.93cm is
E = x 19.5 x 6.93
E = 67.57 J
The more energy needed for the further stretch is
67.57 - 13.55
Energy needed = 54.02 J
Science based on properties of matter and energy
