A free-body force diagram for a heavy wooden bookcase being pushed across a classroom by a student is shown below. (a) Compare the amount of force needed to push the bookcase to the amount of friction force if it is moving at a constant speed. (b) Identify one change to the bookcase or the floor that would affect the amount of force required to move the bookcase. (c) If the amount of force applied by the student is greater than the force of friction, what would you expect the bookcase to do?

Which lists the main components of darwin’s theory of evolution? a. random mutations drive evolution; the evolution of a population happens slowly; organisms have common ancestors; organisms do not change. b. natural selection drives evolution; the evolution of a population happens slowly; organisms have common ancestors; organisms change over time. c. natural selection drives evolution; the evolution of a population happens rapidly; organisms have common ancestors; organisms change over time. d. random mutations drive evolution; the evolution of a population happens rapidly; organisms have common ancestors; organisms do not change.

In which situation has the independent variable for the experiment been changed? check all that apply. changed from counting the number of duckweed at day 0 and day 14 to counting them every day changed from testing duckweed growth in beakers to testing duckweed growth in large outdoor tanks changed from testing the effect of ph on duckweed growth to testing the effect of light levels on duckweed growth changed from testing the effect of acid ph on duckweed growth to testing the effect of basic ph on duckweed growth

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative