Chapter 3, Problem 81RE

A4) The position of a hummingbird flying along a straight line in t seconds is given by S(t) = 2t - 20t meters. [ 1 mark ] (a) Determine the velocity of the bird at t = 3 sec. [0.25 mark] (b) Determine the acceleration of the bird at t = 3 sec. [0.25 mark] (c) Determine the acceleration of the bird when the velocity equals 0. [0.5 mark]

A model rocket is fired vertically upward from rest. Its acceleration for the first three seconds is a(t) = 90t, at which time the fuel is exhausted and it becomes a freely "falling" body. Eighteen seconds later, the rocket's parachute opens, and the (downward) velocity slows linearly to -11 ft/s in 5 seconds. The rocket then "floats" to the ground at that rate. (a) Determine the position function s and the velocity function v (for all times t). 4512 if 0 sts 3 405 if 3 26 15r3 if 0 sts 3 405 if 3 26

A projectile is fired straight up from a platform 10ft above the ground, with an initial velocity of 160 ft/sec. Assume that the only force affecting the motion of the projectile during its flight is from gravity, which produces a downward acceleration of 32 ft/sec?. What is the equation for the height of the projectile above the ground as a function of time t if t = 0 when the projectile is fired? s = -16t2 + 80t + 10 s = 16t2 – 160t + 10 - O D A s = -16t2 – 160t + 10 s = -16t2 + 160t + 10 B