Physics question need help
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Physics question need help

[From: ] [author: ] [Date: 11-10-06] [Hit: ]
How long is it in the air? What is the velocity when it reaches the ground?-The initial speed of the rocket is 45.0 m/s.At its highest point, the speed will be 0.......
A rocket is shot up with an initial speed of 45.0 m/s.
How long does it take the rocket to reach it's highest point? How high does the rocket rise above the ground?

An acorn falls from a branch that is 8.00 meters from the ground. How long is it in the air? What is the velocity when it reaches the ground?

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The initial speed of the rocket is 45.0 m/s. At its highest point, the speed will be 0.0 m/s. The acceleration is -10 m/s due to gravity and you want to find the time. Since we are missing displacement, use the Big Five equation: Final velocity equals initial velocity plus acceleration multiplied by time, or Vf=Vi+at. So, 0 = 45 + (-10)(t). -45 = -10t. Therefore, Time=4.5 seconds. As for the second part, if you substitute the unknown Time for displacement, you can use the equation: Vf(squared) = Vi(squared) + 2a(delta x). In this equation, delta x equals the total distance. So, 0(squared) = 45(squared) + 2(-10)(delta x). 0 = 2025 -20x. -2025 = -20x. Therefore, x = 101.25 meters above the ground.

The given variables for the acorn problem are: x = -8.0 m (because it is falling), initial velocity = 0.0 m/s, acceleration = -10 m/s(squared), and Time is the unknown. Since we are leaving out final velocity, use the equation: delta x = Vit + .5at(squared). -8 = 0(t) + .5(-10)t(squared). -8 = -5t(squared), 1.6 = t(squared). Therefore, Time = 1.3 seconds. To find final velocity, it is easiest to use the equation: Vf = Vi + at. So, Vf = 0 + (-10)(1.3). Therefore, final velocity = -13 m/s.

I hope that helps.
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