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Steph L. - Sep 07, 2007 6:08:58 am PDT #9008 of 10001
the hardest to learn / was the least complicated

1) You are driving a car, and you accelerate from 0 to 25 mph. Say the amount of energy required is x. Now you continue to accelerate from 25 mph to 50 mph. What is the total amount of energy you used to accelerate from 0 to 50 mph?

I want to say it would be more than x, but less than 2x, since you have inertia on your side. Maybe 1.5x?

2) You drop a heavy object from a height of 10 feet, and when it hits the ground it has a velocity of y. What would be the velocity if you drop it from 20 feet? From 40 feet?

Isn't it always y, no matter the height?

Dana - Sep 07, 2007 6:09:32 am PDT #9009 of 10001
"I'm useless alone." // "We're all useless alone. It's a good thing you're not alone."

Would it be weird to close my office door so I could chair-dance to Rage Against the Machine?

tommyrot - Sep 07, 2007 6:10:08 am PDT #9010 of 10001
Sir, it's not an offence to let your cat eat your bacon. Okay? And we don't arrest cats, I'm very sorry.

I'm gonna wait a bit to see if others chime in, then I'll post the answers.

Tom Scola - Sep 07, 2007 6:10:55 am PDT #9011 of 10001
Mr. Scola’s wardrobe by Botany 500

2) You drop a heavy object from a height of 10 feet, and when it hits the ground it has a velocity of y. What would be the velocity if you drop it from 20 feet? From 40 feet?

Don't you need calculus to solve this?

tommyrot - Sep 07, 2007 6:11:13 am PDT #9012 of 10001
Sir, it's not an offence to let your cat eat your bacon. Okay? And we don't arrest cats, I'm very sorry.

Isn't it always y, no matter the height?

Hint: No. Ignoring issues of air friction, a falling object will continue to accelerate, so the farther it falls, the faster it will be going when it reaches the ground.

Daisy Jane - Sep 07, 2007 6:12:09 am PDT #9013 of 10001
"This bar smells like kerosene and stripper tears."

The second one does it much more often. He gets excited when eating, so the only way he can actually eat a meal is if his owners hold him and constantly stroke him to keep him calm.

Awww, puppy!

Dana: No it wouldn't.

tommyrot - Sep 07, 2007 6:12:39 am PDT #9014 of 10001
Sir, it's not an offence to let your cat eat your bacon. Okay? And we don't arrest cats, I'm very sorry.

Don't you need calculus to solve this?

Um, you don't if you know the equation. There is also a trick of geometry (for cases like this) that will let you avoid the calculus.

eta: I think. There is for one part of question 2, at least.

Vortex - Sep 07, 2007 6:13:25 am PDT #9015 of 10001
"Cry havoc and let slip the boobs of war!" -- Miracleman

1) You are driving a car, and you accelerate from 0 to 25 mph. Say the amount of energy required is x. Now you continue to accelerate from 25 mph to 50 mph. What is the total amount of energy you used to accelerate from 0 to 50 mph?

I think that it's 2X, because you can't just go from 25 to 50.

2) You drop a heavy object from a height of 10 feet, and when it hits the ground it has a velocity of y. What would be the velocity if you drop it from 20 feet? From 40 feet?

still y. (9.8 meters per second)

Steph L. - Sep 07, 2007 6:13:45 am PDT #9016 of 10001
the hardest to learn / was the least complicated

Isn't it always y, no matter the height?

Hint: No. Ignoring issues of air friction, a falling object will continue to accelerate, so the farther it falls, the faster it will be going when it reaches the ground.

Curses! Physics triumphs over Tep!Intuition yet again!

Vortex - Sep 07, 2007 6:14:08 am PDT #9017 of 10001
"Cry havoc and let slip the boobs of war!" -- Miracleman

Would it be weird to close my office door so I could chair-dance to Rage Against the Machine?

leave door open. own it.

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