# Simple physics problem

Posted 9 years ago
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 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: 3KgInitial velocity: 250 m/sAngle of launch: 53 Deg.How would something like this be entered?I have looked at examples and am still confused.
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Posted 9 years ago
 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 9 years ago
 Wow. I never would have figured that out. Even with the solution, I have no idea how to enter this into Wolfram.
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