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Simple physics problem

Posted 10 years ago

Greetings all. I just got my son the Pro version to help him in college but he, and I, am having a lot of trouble figuring out how to word and enter problems. For example:

A projectile fired from the ground with the following parameters:

Weight of projectile: 3Kg

Initial velocity: 250 m/s

Angle of launch: 53 Deg.

How would something like this be entered?

I have looked at examples and am still confused.

POSTED BY: Frank Nasuti
2 Replies

Following is a solution of the problem. It requires calculus and some knowledge of Mathematica programming.

In[1]:= g = 9.81;  

In[2]:= (* m value is arbitrary! *)

In[3]:= (* components of initial velocity *)

In[4]:= (* x'[0]=250 Cos[53\[Degree]] *)

In[5]:= (* y'[0]=250 Sin[53 \[Degree]] *)

In[6]:= (* x-motion at constant velocity *)

In[7]:= x[t_] := 250 Cos[53 \[Degree]] t

In[8]:= (*Newton's law for y-motion m y''[t]=-m g*)

In[9]:= DSolve[{m y''[t] == -m g, y[0] == 0, 
  y'[0] == 250 Sin[53 \[Degree]]}, y[t], t]

Out[9]= {{y[t] -> 199.659 t - 4.905 t^2}}

In[10]:= y[t_] := 1/2 (-g t^2 + 500 t Cos[37 \[Degree]])

In[11]:= Solve[y[t] == 0, t]

Out[11]= {{t -> 0. + 0. I}, {t -> 40.7052}}

In[12]:= ParametricPlot[{x[t], y[t]}, {t, 0, 40.7052}]

             Output is plot of parabola
POSTED BY: S M Blinder
Posted 10 years ago

Wow. I never would have figured that out. Even with the solution, I have no idea how to enter this into Wolfram.

POSTED BY: Frank Nasuti
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