hey guy
the vibration per second is frequency
then for 20 vibration time taken is 100 second
in 1 second 20/100 vibration took place
it means 0.2 is frequency
for time period , we have
t=1/f
=1/0.2
=5
We use the formula, to calculate the average speed of the round trip,
Here, 
, is total distance covered by plane in total time, 
.
For the round trip,
.
Thus,
.
An estimated value for gravity at a distance r from the middle of the Earth can be gotten by supposing that the Earth's density is spherically symmetric. The gravity hinge on only on the mass inside the sphere of radius r. All the assistances from outside cancel out as a fall out of the inverse-square law of gravitation. Another result is that the gravity is the same as if all the mass were concentrated at the midpoint. Therefore, the gravitational acceleration at this radius is
g(r) = GM(r) / r²
M(r) = mass enclosed by radius r.
If the Earth had a continual density ρ, the mass would be M(r) = (4/3)πρr³ and the dependence of gravity on distance would be
g(r) = (4/3)πGρr
G = 6.674e-11 m³/kgs²
Answer: Physical is the blank space
Explanation: Your welcome
Question 2.
A transmission system at a radio station consists of essentially the following devices:
1. An oscillator, which converts a direct current into a high-frequency alternating current.
2. A transmitting antenna, which sends out radio waves having the same frequency as the current supplied by the oscillator.
3. A microphone, which picks up the sound waves and converts them into a suitable electric current with the same pattern as the sound waves.
4. A modulator, which enables the waves produced by the antenna to “carry” the pattern of the sound waves picked up by the microphone.
<span>The answer is C. Oscillator</span>
