Answer:
1.29 kg
Explanation:
As we know that
W= FS
1.56 = F (0.78)
F= 1.56/0.78
F= 2 N
Now, According to the definition of Force
F= ma
then
m= F /a
m= 2 / 1.54
m = 1.29 kg
To solve this problem, we have to use the formula:
E = h f
where E is total energy, h is Plancks constant
6.626x10^-34 J s, f is frequency
f = E / h
f = 3.686 × 10−24 J / (6.626x10^-34 J s)
<span>f = 5.56 x 10^9 Hz</span>
Answer:
= 4
Explanation:
To solve this exercise we will use Bohr's atomic model
= - 13.606 / n² [eV]
The transition from level n = 2 to level n = 1 is valid
= - 13.606 [¼ -1/1]
= 10.2045 eV
Bohr's model for atoms with only one electron is
= -13.606 Z² / n²
Where Z is the atomic number of the atom.
In this case the helium atom has an atomic number of Z = 2 from the level n₀ = 2 let's look up to what level it reaches
ΔE = -13.606 [4 /
² - 4/4]
4 /
² = -ΔE / 13.606 + 1
4 /
² = -10.2045 / 13.606 +1 = -0.75 +1
4 /
² = 0.25
= √ 4 / 0.25
= 4
The echo is heard 2.80 s later, this means this is the time the sound takes to travel to the reflecting object and then back to us. So, during this time, the sound wave has covered the distance L between us and the object twice:

The speed of the sound wave is:

, and since it is moving by uniform motion, we can find the distance covered by the wave using

And we said this corresponds to twice the distance between us and the reflecting object, so:

so, the object is 480 meters away.
The best conclusion that can be drawn is that D) A current does not flow in the wire