Homework Help: physics

Posted by help on Wednesday, September 28, 2011 at 3:18pm.

A rocket is fired straight up and accelerates upward at 24 m/s2 for 12 seconds. The rocket then runs out of fuel and coasts. Ignore any air resistance effects and use -9.8 m/s2 for the local acceleration due to gravity.

a) What is the rocket’s maximum altitude?

b) How long is the rocket in the air, from take off until it hits the ground?

c) If the retarding drag chute fails, what is the rocket’s velocity when it hits the ground?
Answer

physics - Henry, Thursday, September 29, 2011 at 7:12pm
a. Vo = at = 24m/s^2 * 12s = 288m/s,

h = (Vf^2 - Vo^2) / 2g,
h = (0 - (288)^2) / -19.6 = 4232m.

b. t(up) = (Vf - Vo) / g,
t(up) = (0 - 288) / -9.8 = 29.4s.
t(dn) = t(up) = 29.4s.
T = t(up) + t(dn) = 29.4 + 29.4=58.8s.
= Time in flight.

c. Vf = Vo(up) = 288m/s.

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