Physics HW 4

[Jess]

Just started so there could be more later on


During a storm, a spherical hailstone with radius r = 1.28 cm falls from a really high cloud. The density of ice is ρice = 920 kg/m³ and that of air is ρair = 1 kg/m³. The air drag coefficient is C=0.88.

(a) What is the speed with which the hailstone hits the ground?

I have the equation to find the velocity (terminal speed) but I can't for the life of me figure out what I'm doing wrong. I've found the mass, given the density and using the volume of a sphere. After a ton of calculating, I still get it wrong.

v = √(mg / CρA)

1.28 cm = 0.0128 m

A = πr²
m = dV

V = (4/3)πr³

[Luminous]

You're hurting my brain.. please..
I really wish I could help, but I stink at physics.
I find that doing the easier questions first kind of warms up my brain, so don't be afraid to just skip hard questions for now and come back to them later.

[Jess]

Hello, can anyone help me? -_-

[teen.jpg]

Hello, can anyone help me? -_-

No, we're all too stupid :rolleyes:

[Jess]

That's a really helpful post...

I still have a few days. Perhaps I'll figure it out myself soon. What I'm doing wrong must be staring at me in the face...

[Syvelocin]

I never took physics. You didn't give work so I can't look at what you did, but 18.72 m/s is what I got (rounded). I might be wrong. I took biology as my science cause it's easier. Just thought I'd try to be semi-helpful.

[Jess]

Nope, not right :/


However, I'm starting to get some clues...

I'm able to do some practice versions, and they give me other values of r. If r is 0.96 (which is less than the real version's, 1.28), the velocity is 11.5. When r is 1.42, v is 13.9...so I'm think it has to be around 12 or something :/

[Jess]

Still stuck. Tried googling the question but got nothing

[TheBigUnit]

Still stuck. Tried googling the question but got nothing

approach you prof during his/her office hours

[Jess]

It's too late. I already submitted the answers.

[Kameraden]

Frankly, you should do your own homework like everyone else. If you need help, refer to your textbook. You gain nothing by asking for hand-outs here.

[Jess]

Frankly, you should do your own homework like everyone else. If you need help, refer to your textbook. You gain nothing by asking for hand-outs here.

I do. I was just asking for assistance. That should be allowed and is allowed. Geez.

[Harley Quinn]

OP request lock. :locked2: