## Hovercraft B/C

Zioly
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### Re: Hovercraft B/C

Zioly wrote:
`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.
Oooohh, I didn't realize that a Newton is how much a kilo can be accelerated! Thanks for the tip!
```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: 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.
Oooohh, I didn't realize that a Newton is how much a kilo can be accelerated! Thanks for the tip!
Yup, right from F=ma

Zioly
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### Re: Hovercraft B/C

Sorry, I thought that since I got it wrong, someone else could have a go at the right answer and put up the next question.

You drop a ball from a 26 meter tall building on earth. Find the velocity when the ball hit the ground. Assume no air resistance and gravity as 9.81. Show all work.
```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:```

RestingDoll
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### Re: Hovercraft B/C

Zioly wrote:Sorry, I thought that since I got it wrong, someone else could have a go at the right answer and put up the next question.

You drop a ball from a 26 meter tall building on earth. Find the velocity when the ball hit the ground. Assume no air resistance and gravity as 9.81. Show all work.
v^2=vi^2+2a(delta_y)
v^2=0-2g(26)
v^2=510.12
v=22.5858 m --> v~23 m
Last edited by RestingDoll on March 13th, 2017, 7:47 pm, edited 1 time in total.

RestingDoll
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### Re: Hovercraft B/C

Zioly wrote:Sorry, I thought that since I got it wrong, someone else could have a go at the right answer and put up the next question.

You drop a ball from a 26 meter tall building on earth. Find the velocity when the ball hit the ground. Assume no air resistance and gravity as 9.81. Show all work.
Wait lol how do I hide it. Edit: nvm, figured it out

Zioly
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### Re: Hovercraft B/C

RestingDoll wrote:
Zioly wrote:Sorry, I thought that since I got it wrong, someone else could have a go at the right answer and put up the next question.

You drop a ball from a 26 meter tall building on earth. Find the velocity when the ball hit the ground. Assume no air resistance and gravity as 9.81. Show all work.
v^2=vi^2+2a(delta_y)
v^2=0-2g(26)
v^2=510.12
v=22.5858 m --> v~23 m
All correct, except for that one little misclick. (You typed "-" instead of "+" in line 2. Your go!)
```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:```

RestingDoll
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### Re: Hovercraft B/C

A small 60 g point mass starts sliding down a frictionless surface at 30 cm in height, then sticks to the end of a uniform rod of mass 120 g and length 40 cm. The rod rotates about a point "O" lengthwise and its moment of inertia about that point is given by 1/3 mr^2. After the point mass sticks to the rod, it pivots to an angle theta, before momentarily stopping. Find theta. (Hint: Don't forget that the potential energy stored after it pivots is based on the center of mass of the entire system.)

Tom_MS
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### Re: Hovercraft B/C

RestingDoll wrote:A small 60 g point mass starts sliding down a frictionless surface at 30 cm in height, then sticks to the end of a uniform rod of mass 120 g and length 40 cm. The rod rotates about a point "O" lengthwise and its moment of inertia about that point is given by 1/3 mr^2. After the point mass sticks to the rod, it pivots to an angle theta, before momentarily stopping. Find theta. (Hint: Don't forget that the potential energy stored after it pivots is based on the center of mass of the entire system.)
`75.5 degrees. If I'm correct, the 1/3mr^2 only matters to determine where the center of mass is.`

RestingDoll
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### Re: Hovercraft B/C

Tom_MS wrote:
RestingDoll wrote:A small 60 g point mass starts sliding down a frictionless surface at 30 cm in height, then sticks to the end of a uniform rod of mass 120 g and length 40 cm. The rod rotates about a point "O" lengthwise and its moment of inertia about that point is given by 1/3 mr^2. After the point mass sticks to the rod, it pivots to an angle theta, before momentarily stopping. Find theta. (Hint: Don't forget that the potential energy stored after it pivots is based on the center of mass of the entire system.)
`75.5 degrees. If I'm correct, the 1/3mr^2 only matters to determine where the center of mass is.`
Interesting... I think you may be forgetting that the center of mass of the system is different than the center of mass of the rod.

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