The refractive index of a material is a dimensionless number that describes how fast light travels through the material. It is defined as n={\frac {c}{v}}, where c is the speed of light in vacuum and v is the phase velocity of light in the medium.
the ratio of the velocity of light in a vacuum to its velocity in a specified medium.
I believe the last one about the bike is correct.
Answer:
When an electric field exists in a conductor a current will flow.
This implies a voltage difference between two points on the conductor.
Electrostatics pertains to static charge distributions.
That means that an object such as a charged spherical conductor will be at the same potential (voltage) on both its outer and inner surfaces.
Explanation:
Given formula:
ME=
mv²+mgh
To make height the subject of the formula, follow the following procedures;
Subtract mv² from both side of equation
M.E - mv² = mv² - mv²+mgh
This gives:
M.E - mv² = mgh
Multiply both sides of the expression by 
( M.E - mv² ) x = x mgh
h = ( M.E - mv² ) x
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Kinetic energy brainly.com/question/6536722
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