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#1 2005-10-08 06:22:08

johndeere147
Member
Registered: 2005-10-08
Posts: 2

Can anyone figure out this word problem?

While sitting around waiting for interior decorators to finish up in the scroll repository, a bunch of bored and mischievous workers decided that they'd build a catapult. When they finally finished, it was able to shoot a projectile straight up into the air. So. in a move which they later regretted, they decided to launch one of the pyramid blocks, which had a density of 2400 kilograms per cubic meter.

When the block crashed back into the catapult, smashing it to pieces, it was determined to have a velocity of 20 meters per second. Assuming that gravity is exactly 9.90 meters per second squared, the block hit the catapult at the same elevation as it was launched from the catapult, and there was, miraculously, no air resistance acting on the block, how high, in centimeters, did the block fly above the catapult? Please round to the nearest centimeter.

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#2 2005-10-08 08:10:03

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Can anyone figure out this word problem?

Yay, a kinematics question!

Take the start point as when the block is fired and the end point as when the block is at its highest point.

We know that the initial velocity is 20ms-¹, the final velocity is 0ms-¹ and the acceleration is -9.9ms-². It shouldn't be, but maybe you're on a different planet or something. I don't know. Anyway, use the constant acceleration equation:

v² = u² + 2as

Rearrange to find s: s = (v²-u²)/2a

Substitute in the values: s = (0-400)/2*-9.9 = 20.202020202020...m.

How lovely. So, your answer is 20.20m to the nearest cm.

The density is irrelevent.

Oh, and by the way, you should be ashamed. Stupid Neopets question cheater type person.


Why did the vector cross the road?
It wanted to be normal.

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#3 2005-10-08 15:25:11

johndeere147
Member
Registered: 2005-10-08
Posts: 2

Re: Can anyone figure out this word problem?

Thanks so much

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