Answer:

Explanation:
Given that,
The speed of an electromagnetic wave traveling in a transparent nonmagnetic substance is given by :

Where
k is the dielectric constant of the substance.
v is the speed of light in water


So, the speed of light in water is 
The strength of the force of friction depends on two factors; the type of surfaces involves and the force that the surfaces are being push together
Explanation:
initial velocity(u) = 90 km/s = 25 m/s
time (t) = 5 sec
mass (m) = 200 kg
final velocity (v) = 0 m/s
v = u + at
0 = 25 + a * 5
-25 = 5 a
-5 = a
Therefore acceleration = -5m/s²
Force = mass * acceleration
F = 200*-5
F = -1000 N
Answer:
Bouyancy
Explanation:
Bouyancy occurs when the upthrust exerted on an object is equal to the weight of object displaced. It is mostly applicable to low density objects for example balloon. When balloon is displaced in water, it floats. This is due to the effect of the upthrust acting on the balloon which allows the balloon to float and which is opposite the weight.
Note that the weight acts downwards the object while the upthrust always acts opposite (upward)
Answer:
They both rises to same height.
Explanation:
When an object is sliding up in friction less surface than according to conservation of energy its potential energy will be converted into kinetic energy.

Here, m is the mass, v is the velocity, g is the acceleration due to gravity and H is the height.
Here the height is independent on the mass of an object and its only depend on velocity.
Now according to the question, two objects have same velocity but they have different masses.
Therefore, they rises to the same height because height will not change with mass.