When you see a tall, young, skinny man walking along the beach, you
observe that a tall, young, skinny man walked along the beach, and from
your observation, you know that a tall, young, skinny man walked along
the beach.
When you see a beach with nobody there, but there is a line of 5-toed
footprints in the sand along the beach, you infer that a human being
walked along the beach. If you are a skilled anthropologist, with some
talent and experience in a few other fields whose names escape me at
the moment, you might be able to make some careful measurements of
the length, width, depth, and shape of the footprints, and then you might
be able to infer that the person who walked along the beach was a tall,
young, skinny man. You would build all of your information from inference,
without any observations at all except for the line of footprints and your
measurements of them.
It depends on how close you get to it. Remember that its gravity decreases as you get farther from it.
We are given the gravitational potential energy and the height of the ball and is asked in the problem to determine the mass of the ball. the formula to be followed is PE = mgh where g is the gravitational acceleration equal to 9.81 m/s^2. substituting, 58.8 J = m*9.8 m/s^2 * 30 m; m = 0.2 kg.
Answer
The refracted wave must obey Snell's equation
Ni sin θi = Nr sin θr
If Nr differs from Ni then sin θr will differ from sin θi
If the wave originates from point A and ends at point B then Snell's Law shows that the time for light to get from point A to point B is a minimum.
