Which of the following is an example of how a scientist might use a model? A wrench is used to tighten a nut onto a piece of wood.

A microscope is used to magnify a group of cells on a slide.

The end of a slinky is moved vertically up and down to simulate a wave.

A stopwatch is used to time the rate of a chemical reaction.

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 0 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)