1. when a particle moves in a circle with constant speed, its acceleration is
a) constantly increasing.
constant in direction.
c) zero.
d) constant in magnitude.
e) constant in magnitude and direction.

During cooling, the kinetic energy of the molecules falls. why does this happen? a.the motion of the molecules increases. b. the motion of the molecules slows down. c.the van der waals forces between molecules decrease d. the forces of attraction between the molecules are overcome.