Simple Kinematics Homework: Find Time & Speed

[calvert11]

Homework Statement

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?

Homework Equations

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

v = v0 + at

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?

 

[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.

 

[calvert11]

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.

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?

 

[Dschumanji]

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?

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?

 

[calvert11]

What would make you think otherwise?

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

 

[Dschumanji]

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

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

 

[calvert11]

Are you doing one of those buggy web assignment things?

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.

 

[Dschumanji]

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.

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.

 

[prateek_34gem]

is answer 1.94s