Help 7,8

7. Use the position function s(t) = t3 - 7t2 + 8t to find the following: (5 pts each) a. Determine when the particle is at rest b. State when the particle is moving forward and backward. Use a sign chart to verify. 8. The range, R, of a projectile is related to the initial velocity, v, and the projection angle, 0, by the equation R = - v2 sin (20 ) where g is the gravitational constant. How is the rate of change of the range related to a change in 0, if v is a constant? (8 pts)