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Bolt falls off rocket, find rocket acceleration

by stangeroo
Tags: acceleration, bolt, falls, rocket
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Apr10-05, 05:36 PM
P: 13
A rocket is launched straight up with constant acceleration. Four seconds after liftoff, a bolt falls off the side of the rocket. The bolt hits the ground 6.70 s later.

Find the rockets acceleration.

I dont understand how to set up this problem, ive never done something like this , asked some friends and they didnt know how to do it. Any help would be greatly appreciated
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Apr10-05, 06:13 PM
P: 787
Work backwards kind of. If it took 6.7 for the bolt to hit the ground, how high was it?

[tex]d = v_{i}t + \frac{1}{2}at^2[/tex]

vi = 0
a = -32 ft\sec^2 or -9.8 m\sec^2
t = 6.7 s

Solve for d.

Now, use the same equation and solve for "a" of the rocket.

[tex]d = v_{i}t + \frac{1}{2}at^2[/tex]

d = part a
vi = 0
t = 4

Doc Al
Apr10-05, 08:10 PM
Doc Al's Avatar
P: 41,476
Do it in two parts, but like this:
Part 1: Find the height and speed of the rocket after 4 seconds in terms of the rocket acceleration. Use:
[itex]h = 1/2 a t^2[/itex] and
[itex]v = a t[/itex]

Part 2: Realize that the initial height and speed of the bolt equals the height and speed of the rocket after 4 seconds (which was calculated in part 1). The height of the bolt after it leaves the rocket is:
[itex]h = h_0 + v_0t -(g/2)t^2[/itex],
using [itex]h_0[/itex] and [itex]v_0[/itex] (in terms of a) from part 1; set h = 0 when t = 6.7 seconds. Solve for a.

Apr10-05, 11:19 PM
P: 13
Bolt falls off rocket, find rocket acceleration

thank you guys

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