It makes an echo and it circles around it.
(a) 
According to Newton's second law, the force experienced by each balloon is given by:
F = ma
where
m = 0.021 kg is the mass
a = 1.1 m/s^2 is the acceleration
Substituting, we found:

The electrostatic force between the two balloons can be also written as

where
k is the Coulomb's constant
Q is the charge on each balloon
r = 16 m is their separation
Since we know the value of F, we can find Q, the magnitude of the charge on each balloon:

(b)
electrons
The magnitude of the charge of one electron is

While the magnitude of the charge on one balloon is

This charge can be written as

where N is the number of electrons that are responsible for this charge. Solving for N, we find:

Answer:
1.34352 kg
Explanation:
= Mass of water falling = 1 kg
h = Height of fall = 0.1 km
= Change in temperature = 0.1
c = Specific heat of water = 4186 J/kg K
g = Acceleration due to gravity = 9.81 m/s²
= Mass of water in the vessel
Here the potential energy will balance the internal energy

Mass of the water in the vessel is 1.34352 kg
Answer:
Mass and volume.
Explanation:
The equation for density is always mass divided by volume. To determine the density of a fluid, you would need to find its volume and its mass.