On a sunny day, the concrete at the side of the pool feels much hotter than the water even though both have received the same thermal energy from the sun. explain fully why the concrete is hotter? (2)

In this experiment, you will use a track, a toy car, and some washers to explore newton’s first two laws of motion. you will make observations and collect data regarding the motion of these objects. in the space below, write a general scientific question that you will answer by doing this experiment.

In a hydrogen molecule there are a total of four charges, 2 protons in the two nuclei, and 2 electrons. how many unique charge-pairs are there (without double counting)?

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".