Calculating Projectile Height with Position Function | Physics Tutorial

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To calculate the height of a ball thrown upward at 64 ft/sec from an initial height of 80 ft, one must derive the position function using the equations of motion under constant gravity. The process involves integrating the vertical acceleration, a(t), to find the vertical velocity, v(t), and then integrating v(t) to obtain the vertical displacement, z(t). The equations are v(t) = gt + v_0 and z(t) = (1/2)gt^2 + v_0t + z_0, where g represents gravitational acceleration. Initial conditions, such as initial velocity and height, are used to determine the constants v0 and z0. This method provides a comprehensive way to model projectile motion in a gravitational field.
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If a ball is thrown upward at 64 ft/sec at an initial height of 80 ft, how would you get the position function that finds the height as a function of t? Do you just integrate?

Thanks :smile:
 
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Of course.Or you may use the equation of motion for a constant gravity field.

Daniel.
 
courtrigrad said:
If a ball is thrown upward at 64 ft/sec at an initial height of 80 ft, how would you get the position function that finds the height as a function of t? Do you just integrate?
What are you proposing to integrate?

AM
 
One would actually integrate TWICE. For this single "z" dimensional problem, one would use:

v(t) = \int a(t) dt

z(t) = \int v(t) dt

where a(t) is vertical acceleration, v(t) vertical velocity, and z(t) vertical displacement. Given constant gravitational acceleration a(t)=g, this would yield:

v(t) = \int g dt \ = gt + v_0

z(t) = \int (gt + v_0) dt \ = (1/2)gt^2 + v_0t + z_0

Initial conditions would determine constants v0 and z0.

~
 
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