Homework Help: physics

Posted by Jen on Sunday, January 16, 2011 at 6:11pm.

A model rocket leaves the ground, heading straight up at 47 m/s.
(a) What is its maximum altitude?
m
What are its speed and altitude at each of the following times?
(b) 1 s
m/s
m
(c) 4 s
m/s
m
(d) 8 s
m/s
m

physics - Henry, Monday, January 17, 2011 at 7:39pm
a. When h = hmax, Vf = 0.

(Vf)^2 = (Vo)^2 + 2gh = 0,
(47)^2 + 2(-9.8)h = 0,
2209 - 19.6h = 0,
-19.6h = -2209,
h = -2209 / -19.6 = 112.7m.

b. V = Vo + gt,
V = 47 + (-9.8)1,
V = 47 - 9.8 = 37.2m/s.

h = Vo*t + 0.5gt^2,
h = 47*1 + 0.5(-9.8)1^2,
h = 47 - 4.9 = 42.1m.

c. Same procedure as b except t = 4s.

d. Same procedure as b, and c except
t = 8s and g = +9.8.

NOTE: g = + 9.8 for all values of t above 4.8 because the rocket is falling.

seconds because the rocket is

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