You drop a ball from a height of 10 meters. Each time the ball bounces, it reaches a lower height. Why does the ball lose height after each time it hits
the ground?
A. Some of its kinetic energy is transformed into thermal energy
because of friction between the floor and ball.
B. Some of its kinetic energy is transformed into potential energy
each time bounces upward.
O
C. Some of its potential energy is transformed into kinetic energy
each time it falls.
D. Some of its thermal energy is transformed into potential energy by
the force of gravity each time it bounces.

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".