What is the observed concept known as? (When light doesn't reflect or refract due to it being in a 90 degree angle and it is positioned where the two mediums are parallel to it)

What is the freezing point of radiator fluid that is 50% antifreeze by mass? kf for water is 1.86 ∘c/m.

Astone is dropped from the upper observation deck of a tower, 250 m above the ground. (assume g = 9.8 m/s2.) (a) find the distance (in meters) of the stone above ground level at time t. h(t) = (b) how long does it take the stone to reach the ground? (round your answer to two decimal places.) s (c) with what velocity does it strike the ground? (round your answer to one decimal place.) m/s (d) if the stone is thrown downward with a speed of 2 m/s, how long does it take to reach the ground? (round your answer to two decimal places.) s

Which if the following types of research is conducted on multiple occasions over time