an athlete swims the length L of a pool in a time t1, and make the return trip to the starting position in a time t2. if they are swimming initially in the positive x-direction, determine their average velocities symbolically in (a) at the first half of the swim, (b) the second half of the swim and (c) the round trip. (d) what is their average speed for the round trip?

The necleus of an atom is made up of what subatomic particles?

Why does lightning travel from clouds to the ground?

Emmy kicks a soccer ball up at an angle of 45° over a level field. she watches the ball's trajectory and notices that it lands, two seconds after being kicked, about 20 m away to the north. assume that air resistance is negligible, and plot the horizontal and vertical components of the ball's velocity as a function of time. consider only the time that the ball is in the air, after being kicked but before landing. take "north" and "up" as the positive ‑ and ‑directions, respectively, and use ≈10 m/s2 for the downward acceleration due to gravity.