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Dynamics ?

by 2slowtogofast
Tags: dynamics
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2slowtogofast
#1
Feb10-09, 09:52 PM
P: 132
When Vo=68 ; k=.027 ; theta = 39 degrees

(a) The American Football kicker lines up to attempt a field goal . Take the balls initial position to be the origin. For the field goal to be good it must pass between the upstairs, and over the crossbar which are 10 feet above ground level. Assuming the ball is kicked straight ( directly between the upright ), and the ball is given an initial velocity of Vo at an angle theta answer the following questions.

(a)What is the maximum field goal distance for this kicker if you ignore all drag forces.

I solved (a) to be 126.64 in the x direction.

(b) If we include a crude model for the drag force in which the net acceleration on the ball is given by:
a=(-k * vx ) i + (-g -k * Vy) j ( ft/s2 )

Derive the equations describing the horizontal and vertical positions as functions of time.


- I am lost when I get to (b) and also i couldt get the picture to load but its basicly a football x yards away from a goal post 10 ft in the air. im just confused on how to start this off my teacher said there would be a few integrals in this problem and i tried relating

a = dv/dt solving for v then v = ds/dt for each component but it didt work

the vx and vy are velocity in x nd veloctiy in y i just couldt get the subscipts on this computer im on
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2slowtogofast
#2
Feb10-09, 11:18 PM
P: 132
anybody have any ideas
nvn
#3
Feb11-09, 08:20 AM
Sci Advisor
HW Helper
P: 2,121
2slowtogofast: Perhaps try thread 291331.


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