# Homework Help: Simple Kinematics

1. Sep 19, 2008

### calvert11

1. The problem statement, all variables and given/known data

A hot air balloon is traveling vertically upward at a constant speed of 4.4 m/s. When it is 27 m above the ground, a package is released from the balloon.

The acceleration of gravity is 9.8 m/s^2.

a) After it is released, for how long is the package in the air.

b) What is its speed just before impact with the ground?

2. Relevant equations

x = x0 + v0t + 1/2at^2

v = v0 + at

3. The attempt at a solution

a)

0 = 27 + 4.4t + 1/2(-9.8)t^2
t = 2.839 s ***this answer is wrong.

Is it wrong because v0 should equal 0 and not 4.4?

b)

v = 4.4 - 9.8(2.839)
v = -23.42 m/s ***this answer is obviously wrong because t is wrong.

But, should v0 be zero in this case as well?

2. Sep 19, 2008

### Dschumanji

I don't see anything wrong with your algebra in part (a) and (b). The only problem I see is your rounding of sig figs.

3. Sep 19, 2008

### calvert11

Sig figs don't matter in the answer. In fact, answers are encouraged to be 6 figures long (though less is still acceptable).

But you don't agree that v0 = 0 in this problem?

4. Sep 19, 2008

### Dschumanji

The package does indeed have an initial velocity of 4.4m/s if you are measuring it from the ground which it seems the problem is doing throughout.

What would make you think otherwise?

5. Sep 19, 2008

### calvert11

No, I agree with you. It's just, I'm still being told it's the wrong answer. But thank you for your help.

6. Sep 19, 2008

### Dschumanji

Who or what is telling you it is wrong? Are you doing one of those buggy web assignment things?

7. Sep 19, 2008

### calvert11

Yes, it's a web assignment. But, like you said, the problem is set up correctly?

So, I'm guessing it's a tech problem. Again, thanks for the help.

8. Sep 19, 2008

### Dschumanji

Do you have to input both answers in the same line? The problem might be the fact that part b asks for the speed and you are giving the velocity.

9. Sep 21, 2008