## Hovercraft B/C

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### Re: Hovercraft B/C

sciduck wrote:
sciduck wrote:
```From Bernoulli's principle, I get a velocity of 4.427 m/s.
Let's say that's horizontal velocity, so initial vertical velocity is 0 m/s.
So it'll take 1.01015 s to hit the ground.
No horizontal velocity --> 4.6047 m.
Uhhh, 1 sigfig? So ~5m.```
Yeah, sorry about the sigfigs, I was just throwing numbers at it. I was with you until the final step, where x = vt = 4.427 m/s * 1.01015s = 4.472m
Oops, I typed it in my calculator wrong ;a;

Next question: Say you are standing on top of a building and threw a ball A downward with a velocity -v, and threw a different ball B (from the same height) upward with a velocity of v. Then:
A) A will hit the ground with a velocity greater than B's.
B) B will hit the ground with a velocity greater than A's.
C) Both hit the ground at the same speed.
D) Neither of the balls will hit the ground.
`The answer is C. Because the two balls have the same initial total energy (gravitational potential+kinetic) they will have the same kinetic energy when gravitational potential energy is 0 and will therefore have the same velocity. Lol at answer D though.  :lol:`
Last edited by HandsFreeCookieDunk on March 1st, 2017, 8:28 pm, edited 1 time in total.

Ashernoel
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### Re: Hovercraft B/C

sciduck wrote:
sciduck wrote:
```From Bernoulli's principle, I get a velocity of 4.427 m/s.
Let's say that's horizontal velocity, so initial vertical velocity is 0 m/s.
So it'll take 1.01015 s to hit the ground.
No horizontal velocity --> 4.6047 m.
Uhhh, 1 sigfig? So ~5m.```
Yeah, sorry about the sigfigs, I was just throwing numbers at it. I was with you until the final step, where x = vt = 4.427 m/s * 1.01015s = 4.472m
Oops, I typed it in my calculator wrong ;a;

Next question: Say you are standing on top of a building and threw a ball A downward with a velocity -v, and threw a different ball B (from the same height) upward with a velocity of v. Then:
A) A will hit the ground with a velocity greater than B's.
B) B will hit the ground with a velocity greater than A's.
C) Both hit the ground at the same speed.
D) Neither of the balls will hit the ground.
```Answer:
C.
Velocity is a vector, and by throwing A down with -v, it can be translated to upward with v, the same as B. then due to acceleration due to gravity, both will follow the same trajectory and hit the ground at the same time```
Last edited by Ashernoel on March 1st, 2017, 9:00 pm, edited 2 times in total.
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### Re: Hovercraft B/C

Ashernoel wrote:
sciduck wrote:
Yeah, sorry about the sigfigs, I was just throwing numbers at it. I was with you until the final step, where x = vt = 4.427 m/s * 1.01015s = 4.472m
Oops, I typed it in my calculator wrong ;a;

Next question: Say you are standing on top of a building and threw a ball A downward with a velocity -v, and threw a different ball B (from the same height) upward with a velocity of v. Then:
A) A will hit the ground with a velocity greater than B's.
B) B will hit the ground with a velocity greater than A's.
C) Both hit the ground at the same speed.
D) Neither of the balls will hit the ground.
```C.
Velocity is a vector, and by throwing A down with -v, it can be translated to upward with v, the same as B. then due to acceleration due to gravity, both will follow the same trajectory and hit the ground at the same time```
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Ashernoel
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### Re: Hovercraft B/C

`thanks for the help, this is pretty sick :p`
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sciduck
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### Re: Hovercraft B/C

sciduck wrote:
Yeah, sorry about the sigfigs, I was just throwing numbers at it. I was with you until the final step, where x = vt = 4.427 m/s * 1.01015s = 4.472m
Oops, I typed it in my calculator wrong ;a;

Next question: Say you are standing on top of a building and threw a ball A downward with a velocity -v, and threw a different ball B (from the same height) upward with a velocity of v. Then:
A) A will hit the ground with a velocity greater than B's.
B) B will hit the ground with a velocity greater than A's.
C) Both hit the ground at the same speed.
D) Neither of the balls will hit the ground.
`The answer is C. Because the two balls have the same initial total energy (gravitational potential+kinetic) they will have the same kinetic energy when gravitational potential energy is 0 and will therefore have the same velocity. Lol at answer D though.  :lol:`
Yup! I lost track of turns, but go for it.
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### Re: Hovercraft B/C

Shamelessly copied from the internet....

According to the Guinness Book of World Records, the fastest recorded baseball pitch was delivered by Nolan Ryan in 1974. The pitch was clocked at 100.9 mi/hr (45.0 m/s). Determine the impulse required to give a 0.145-kg baseball such a momentum.

Zioly
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### Re: Hovercraft B/C

HandsFreeCookieDunk wrote:Shamelessly copied from the internet....

According to the Guinness Book of World Records, the fastest recorded baseball pitch was delivered by Nolan Ryan in 1974. The pitch was clocked at 100.9 mi/hr (45.0 m/s). Determine the impulse required to give a 0.145-kg baseball such a momentum.
```Impulse is known as the change in momentum over time. The impulse-momentum theory states that J=Δp.

So,

J=(0.145 kg*45 m/s)-(0.145 kg*0 m/s)
J=6.525 kg*m/s - 0 kg*m/s
J=6.525N - 0N
J=6.525N```
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### Re: Hovercraft B/C

Zioly wrote:
HandsFreeCookieDunk wrote:Shamelessly copied from the internet....

According to the Guinness Book of World Records, the fastest recorded baseball pitch was delivered by Nolan Ryan in 1974. The pitch was clocked at 100.9 mi/hr (45.0 m/s). Determine the impulse required to give a 0.145-kg baseball such a momentum.
```Impulse is known as the change in momentum over time. The impulse-momentum theory states that J=Δp.

So,

J=(0.145 kg*45 m/s)-(0.145 kg*0 m/s)
J=6.525 kg*m/s - 0 kg*m/s
J=6.525N - 0N
J=6.525N```
`The units of impulse are N*s.`

Zioly
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### Re: Hovercraft B/C

Zioly wrote:
HandsFreeCookieDunk wrote:Shamelessly copied from the internet....

According to the Guinness Book of World Records, the fastest recorded baseball pitch was delivered by Nolan Ryan in 1974. The pitch was clocked at 100.9 mi/hr (45.0 m/s). Determine the impulse required to give a 0.145-kg baseball such a momentum.
```Impulse is known as the change in momentum over time. The impulse-momentum theory states that J=Δp.

So,

J=(0.145 kg*45 m/s)-(0.145 kg*0 m/s)
J=6.525 kg*m/s - 0 kg*m/s
J=6.525N - 0N
J=6.525N```
`The units of impulse are N*s.`
Sorry about that, but wouldn't it be N/s? Also, what unit is momentum in? I had a question on a test the other day and was uncertain... as you can tell, impulse and momentum are concepts I'm not as familiar with.
```Bottle Rockets: 5th
Ecology: 9th
Hovercraft: 14th
Scrambler: 29th (with a failed run too  ;))```
```Mousetrap Vehicle
Hovercraft
Ecology
Experimental Design (or other inquiry :P)

...Yes, my profile picture is G2 apEX at the PGL Major Qual.  :lol:```

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### Re: Hovercraft B/C

Zioly wrote:
Zioly wrote:
```Impulse is known as the change in momentum over time. The impulse-momentum theory states that J=Δp.

So,

J=(0.145 kg*45 m/s)-(0.145 kg*0 m/s)
J=6.525 kg*m/s - 0 kg*m/s
J=6.525N - 0N
J=6.525N```
`The units of impulse are N*s.`
Sorry about that, but wouldn't it be N/s? Also, what unit is momentum in? I had a question on a test the other day and was uncertain... as you can tell, impulse and momentum are concepts I'm not as familiar with.
No, it's N*s. As you said, the unit of momentum is kg*m/s. Since Impulse is the change in momentum, it will have the same unit. A Newton is kg*m/s^2. Therefore, the unit for momentum is the Newton times a unit of time.

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