Please help me in my physics homework...?

Question

a baseball leaves the bat with a speed of 34m/s at an angle of 37degrees above the horizontal. the ball is 1.2m off the ground when it leaves the bat. to be a home run, the ball must clear a fence that is 3meters high and 106meter from the batter. A.)At what times after being hit will it reach the height of the fence? B.)how far from the batter will the ball be at these times? C.) will the batter4 have a home run?explain.

Answer 1

You can do this using what my professors call an up, down and out method of mechanical physics, set up a chart like this:

   up | down | out

a

v1

v2

d

t

a=acceleration v=velocity d=distance t=time, a will be 9.8 m/s for up and down, except up will be negative, and there wont be any acceleration for out because horizontal has none.  V1 is your initial velocity, and v2 is your final velocity, there will only be one velocity for out, but for up, v1=?, v2=0 (because it has to stop before it can fall again) and for down, v1=0(its stopped before it falls) and v2=?.  You can figure out the velocity up and out by using the 34 m/s you are given and putting it into a right triangle, to get the equations v1(up)= 34*sin(37) and v(out)=34*cos(37).  

To find out all of the numbers, there are a handful of equations you can use, I don't remember them off hand, however I'm sure they are in your notes or textbook.

a)  find out the t value for d=3 for up and down both, they will be the answer

b)  find the d value for out using the times you got in a.

c)  If the distance out is over 106 meters at the same time that the distance down is 3 meters above ground, (you should already have this info from part b)  then its a home run.  

Good luck