Answer:
Ro = 7.8 [g/cm³]
Explanation:
According to the principle of Archimedes, the volume of a body immersed in a liquid is equal to the volume displaced by water. That is, in this problem The displacement volume is equal to the new volume minus the original volume.
![V_{n}=110[cm^{3} ]\\V_{o}=100[cm^{3} ]\\V_{d}=110-100 = 10 [cm^{3} ]](https://tex.z-dn.net/?f=V_%7Bn%7D%3D110%5Bcm%5E%7B3%7D%20%5D%5C%5CV_%7Bo%7D%3D100%5Bcm%5E%7B3%7D%20%5D%5C%5CV_%7Bd%7D%3D110-100%20%3D%2010%20%5Bcm%5E%7B3%7D%20%5D)
We now know that density is defined as the relationship between mass and volume.

where:
Ro = density [g/cm³]
m = mass = 78 [g]
Vd = displacement volume [cm³]
![Ro = 78/10\\Ro = 7.8 [g/cm^{3} ]](https://tex.z-dn.net/?f=Ro%20%3D%2078%2F10%5C%5CRo%20%3D%207.8%20%5Bg%2Fcm%5E%7B3%7D%20%5D)
The electric field is given by volts/distance:

. The breakdown voltage of dry air is about 3x10^6V/m. So solving for V we get

or
If the runner is running in a circular track then yes when something or someone is moving in a circular motion at a constant speed they are indeed accelerating. They’re accelerating because the direction of the velocity vector is changing