# Homework Help: Urgent help needed on physics problem

1. Sep 30, 2004

### mattmaka

Urgent help needed on physics problem!!!

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 6.40 s later.

What is the rocket's acceleration?

2. Sep 30, 2004

### mattmaka

I have no idea how to relate the distances or anything. Any help in setting up equations would be great.

3. Sep 30, 2004

### vsage

Ok I made a little mistake before. R is the rocket's acceleration so the displacement for the first 4 seconds is d0 = 0.5 * R * 4^2 = 8R. The velocity it gains during this time is equal to R*T = 4R

Now during the drop the displacement is given by d = d0 + v1*t + 0.5*(-g)*t^2

At t = 6.4 seconds d and d0 are equal. Subbing in some stuff and knowing that d = 0 after 6.4 seconds 0 = 8R + 4R*6.4 - 4.9*6.4^2. Solve for R.

Last edited by a moderator: Oct 1, 2004
4. Sep 30, 2004

### tony873004

5.95 m/s^2

5. Sep 30, 2004

### Thaore0

How did you get the answer tony?

6. Sep 30, 2004

### tony873004

I wrote a computer program, trying different values for a, until t = 10.4
Code (Text):

Private Sub Command1_Click()
Dim a As Double, Vrocket As Double, Vbolt As Double, pRocket As Double, pBolt As Double
Dim t As Double, sstep As Double

sstep = 0.01
pRocket = 0
Vrocket = 0
a = 5.95

For t = 0 To 4 Step sstep
Vrocket = Vrocket + a * sstep
pRocket = pRocket + Vrocket
Next t

pBolt = pRocket
Vbolt = Vrocket
t = 4 + sstep

While pBolt > 0
Vbolt = Vbolt - 9.81 * sstep
pBolt = pBolt + Vbolt
t = t + sstep
Wend
Text1.Text = t
End Sub

7. Sep 30, 2004

### Thaore0

Sweet! Is that Visual Basic?

8. Sep 30, 2004

### tony873004

Yes, VB 6.0. That's how I do the problems I can't quite understand. It's called a numerical solution. There are some problems where no analytical solution exists, and a numerical solution is necessary.

But I'm sure that an analytical solution exists for this problem, and I'm waiting to see if someone knows it. This is the type of problem I'm going to face in about 2 weeks. (And I'm not allowed to bring my laptop to tests )

9. Oct 1, 2004

### vsage

Read my post above sorry I posted an incorrect solution before it's about 5.96.

10. Oct 1, 2004

### mattmaka

thanks for the help guys.

11. Oct 1, 2004

### tony873004

Did you get it right? I imagine you're using an instant grading homework system?