An object is moving east, and its velocity changes from 65 m/s to 25 m/s in 10 seconds. Which describes the acceleration?

negative acceleration of 4 m/s2
positive acceleration of 4 m/s2
positive acceleration of 9 m/s2
negative acceleration of 9 m/s2

a:

by the combination of an unlimited number of elements

frequency, z, and the collision density, z, in carbon dioxide (co2), r 180 pm at 30 °c and 120 kpa

nuclear fission produces elements that are heavier than helium.

the elements that are used in nuclear fission and their products are much heavier than helium.