mt2568

If you know how to do these, please either answer them here or catch me on AIM: Tregaron2002

1. For an object falling freely from rest, show that the distance traveled during each successive second increases in the ration of successive odd integers.

2. A fall stone takes .30 seconds to travel past a window 2.2 m tall. From what height above the top of the window did the stone fall?

3. Suppose you adjust your garden hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (the hose is 1.5 m off the ground). When you quickly move the nozzle from the vertical you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?

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mt2568

Problems 1 and 2 have been answered, but number three still alludes me...

mt2568

eludes not alludes, hehe

enigma

Staff Emeritus
Gold Member
Welcome to the forums,

Think of the water's sound stopping as the time when the last of the water finished it's motion.

You can model the last of the water as a particle, then.

You have the total time, angle, starting height, ending height, and gravity. Solve for velocity.

Does that make sense, or do you need more?

BTW: for help in homework on these forums, we ask that you show your work and where you got stuck.

mt2568

This how I got my answer, not sure if it was right though...

v = V0T + 2AT^2 (2nd Kinematic equation)

x-1.5 = v0(2s) + 2(9.8m/s^2)(2s)

When T = 2, then x- 1.5 is zero (When the water hits the gound the velocity of the water is zero)

v0 = -19.6m/s or 19.6 m/s

mt2568

Actually forgot to divide that 2s, its 9.6 m/s

mt2568

Also forgot that one part is .5 not 2, i wrote it wrong but still calculated with the .5

Antiproton

I also got 9.65 (remember those sig figs!!!). Congratulations on this problem. Keep up the hard work.

kay2500

Isn't the second kinematic equation (1/2)AT^2 instead of 2AT^2?

Antiproton

Yes, it is. But he found his mistake and corrected it. Using 1/2 instead of 2, he got the appropriate answer.

kay2500

Oh, right. Heh, sorry, I didn't notice that.

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