Listena bicycle and its rider have a combined mass of 80. kilograms and a speed of 6.0 meters per second. what is the magnitude of the average force needed to bring the bicycle and its rider to a stop in 4.0 seconds?
a.1.2 × 102 n
b.3.2 × 102 n
c.4.8 × 102 n
d.1.9 × 103 n

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.