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A point charge is placed 3 m from a 4 µC charge. What is the strength of the electric field on the point charge at this distance
2 answers:
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The box is kept in motion at constant velocity by a force of F=99 N. Constant velocity means there is no acceleration, so the resultant of the forces acting on the box is zero. Apart from the force F pushing the box, there is only another force acting on it in the horizontal direction: the frictional force 
which acts in the opposite direction of the motion, so in the opposite direction of F.
Therefore, since the resultant of the two forces must be zero,
so
The frictional force can be rewritten as
where
, 
. Re-arranging, we can solve this equation to find 
, the coefficient of dynamic friction:
Therefore, since the resultant of the two forces must be zero,
so
The frictional force can be rewritten as
where
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