Because plastic and rubber are known as insulators which keep metal wires protected
Answer:
Frequency = 658 Hz
Explanation:
The third harmonics of A is,

The second harmonics of E is,

The difference in the two frequencies is,
delta_f = 1320 Hz - 1318 Hz = 2 Hz
The beat frequency between the third harmonic of A and the second harmonic of E is,
delta_f = 

We have calculate the frequency of the E string when she hears four beats per second, then
delat_f = 4 Hz


Hope this helps!
Answer:
Since your spine runs by your core, having a strong core will help protect and stabilize your spine, and you're also are able to control movements such as walking or standing better with a strong core.