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Old Mar 24th 2011, 01:22 AM   #1
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Verticle projectile - check my work?

Hi, have I got this correct?

An object is projected directly upwards and 0.2 seconds after launch it has reached a height of 0.57 meters.

A) What is the initial speed as it lifts off the ground?
B) What is its speed at a height of .57 meters?
c) How much higher does it go?

A)
X-X0 = V0t + 0.5At^2
0.57-0 = V0(0.2) -4.9(0.2)^2
0.57 + 0.196 = V0(0.2)
V0 = 0.766/0.2
V0 = 3.83M/S

B)
V = V0 + At
V = 3.83 + (-9.8)(0.2)
V = 1.87M/S

C)
V^2 = V0^2 + 2A(X-X0)
0 = 3.83^2 + 2(-9.8)(X-0)
-14.6689 = -19.6(X)
X =
-14.6689/-19.6
X = 0.7484m (Maximum height)
0.7484 - 0.57 = The object travels 0.1784m higher than the height achieved at the 0.2 second mark.


Thanks
Splint

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Old Mar 24th 2011, 04:25 AM   #2
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Don't see any errors straight up.
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Old Mar 24th 2011, 10:09 AM   #3
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@ Splint This might seem to be a little picky, but it's important none the less. Physics is "case sensitive." That is to say, for example, the symbol for acceleration is not "A" it is "a." Different meanings are attached to the two symbols. (A usually stands for an amplitude of a wave, and a is an acceleration.) The same comment applies to units. The unit for velocity is not "M/S" it is "m/s."

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