Answer:
The distance that you marginally able to discern that there are two headlights rather than a single light source is 6.084 km
Explanation:
Given:
d = distance = 0.679 m
λ = wavelength of the light = 537 nm = 537x10⁻⁹m
dp = pupil diameter = 4.81 mm = 0.00481 m
Question: What distance, in kilometers, are you marginally able to discern that there are two headlights rather than a single light source, dx = ?
For the separation of the peak from the central maximum it is:

In this case, the two small sources of the headlights have the same angle as the images that form inside the eye

On foot= 1 kilometer per 5 minutes
Bike= I kilometer per 2 minutes
3 minutes fast per mile on bike
Mechanical energy E = mgh + 1/2mv²
When he starts, let h = 0 ⇒ E₁ = 1/2mv₁²
When he reaches height h ⇒ E₂ = mgh + 1/2mv₂²
Without friction, energy is conserved at all times.
E₁ = E₂
↓
1/2mv₁² = mgh + 1/2mv₂²
↓
1/2v₁² = gh + 1/2v₂²
↓
gh = 1/2(v₁² - v₂²)
↓
h = (v₁² - v₂²) / (2g)
This may shock you:
We NEVER feel speed, velocity, or motion, as long as it's constant.
We only feel CHANGES in speed, velocity, or motion.
That means speeding up, slowing down, or changing direction.
As long as we're moving in a straight line at a constant speed, we don't feel anything.