(a) Force between the two charges
The electrostatic force between the two charges is given by:

where k is the Coulomb's constant, q1 and q2 the two charges, r their separation.
In this problem:



Substituting into the equation, we find

(b) direction of particle q2
Particle q2 wants to move in the direction of the force acting on it. The direction of the force depends on the relative sign of the two charges: like charges attract each other, opposite charges repel each other. In this case, the two charges are both positive, so they repel each other and q2 tends to move away from particle q1.
1/f= 1/di+1/do
1/f=1/90m+1/40m
1/f ≈27.7m
Answer:
560 m
Explanation:
The speed of sound in air is approximately:
v ≈ v₀ + 0.6T
where v₀ is the speed of sound at 0°C (273 K) in m/s, and T is the temperature in Celsius.
The speed of sound at 20°C at that altitude is:
v ≈ 327 + 0.6(20)
v ≈ 339 m/s
The sound travels from the hikers to the mountain and back again, so it travels twice the distance.
339 m/s = 2d / 3.3 s
2d = 1118.7 m
d = 559.35 m
Rounding, the mountain is approximately 560 m away.
A. the same speed as the wave energy
Distance and time, distance because that's how far and time because that's how long