       Re: newbie here,, need help with parametrics

• To: mathgroup at smc.vnet.net
• Subject: [mg96553] Re: newbie here,, need help with parametrics
• From: Scott Hemphill <hemphill at hemphills.net>
• Date: Mon, 16 Feb 2009 06:57:42 -0500 (EST)
• References: <gn5u3e\$gko\$1@smc.vnet.net>
• Reply-to: hemphill at alumni.caltech.edu

```"R.J." <nemocamaro at epix.net> writes:

> I am using Mathematica and i'd rather be using derive,,,,, but anyways,,  heres the problem i have to do, a baseball is thrown from the stands 32 feet from the ground at an angle of 30 degrees above the horizontal, initial velocity is 32 feet per second.
>
> what i want to do is find how to plot this in mathematica,, the graph i keep getting says it hits the ground after .8 seconds,   and i know thats not right,,, here is the formula i am using
>
> r = (x + v Cos a) t) i + (y + (v Sin a) t - 1/2 gt^2) j
>
> where x is the initial x position and y is the initial height, v is the initial velocity a is the angle (30*) t is time and g is the gravitational constant..
>
> i'm stuck,,, any help?

Your equation doesn't have balanced parentheses.  If you had posted
your actual Mathematica code, then we would know what you did wrong.
Since you didn't, we can only guess.

My guess is that you gave the angle as "30", which means 30 radians,
instead of "30 Degree" or "Pi/6" which would mean 30 degrees.

An angle of 30 radians would mean a throw which is almost straight
down, so it would take less than a second to cover the 32 foot
vertical distance with an initial velocity of 32 feet/sec.

Scott
--
Scott Hemphill	hemphill at alumni.caltech.edu
"This isn't flying.  This is falling, with style."  -- Buzz Lightyear

```

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