In a disaster at sea, life vests (also called personal floatation devices, or PFDs) can save lives. If you were to design a PFD, what material would you use? Why? Be sure to
use the word "density" in your explanation. You may use internet resources to answer
this question. (2 sentences)

An object moves from position +34m to the position -15m in 15 seconds. what is the total displacement? what is the total velocity?

The astronauts on the space shuttle flights experienced an acceleration of 29 m/s2 (about 3 "g's") during lift-off. what upward force must the astronaut's seat apply to the astronaut in order to cause this acceleration? assume the astronaut's mass is 70 kg, and compute this force when the acceleration is near the earth's surface so their weight equals latex: mg m g .

Which of the following is a measure of the amount of light a star directly emits?               a.  luminosity    b.  intensity    c.  wavelength    d.  brightness