plzzz hurrryyy!!!! its simple...!!!

lapachacha

hello people...i have beeen given this projectile problem to be solved numerically in FORTRAN..i have coded it using runge0kutta 4th order ......now the thing is that i have not been given the end points of time,,;ie. the range.. and i am asked to

a)the maximum height attained by the projectile

what is to b added to the existing code to achive this?

b)the time required to reach the maximum height

what is to b added to the existing code to achive this?

c)the time required to return to the original elevation..

what is to b added to the existing code to achive this?

i did fortran 4 years ago...havent beeen in practice..this was the lone effort i cud recall...please help...


i have attached the question and the code..

heres the code
CODE


!************************************************* *********************
! *
! projectile question *
! *
!************************************************* **********************


DATA M,G,C/10.0,9.80665,0.1/

!FIRST i HAVE REDUCED THE GIVEN EQUATION IN TWO LINEAR 1ST-ORDER EQUATIONS
!FOR THE SOLUTION TO PROCEED


F1(T,U1,Y2) = U1
F2(T,U1,Y2) = (-M*G-C*U1**2)/M


!ASSIGNMENT OF VALUES TO CONSTANTS



WRITE(*,*) 'Input left and right endpoints separated by'
WRITE(*,*) 'blank'
WRITE(*,*) ' '
READ(*,*) A, B

WRITE(*,*) 'Input the two initial conditions.'
WRITE(*,*) ' '
READ(*,*) ALPHA1, ALPHA2

WRITE(6,*) 'Input a positive integer for the number'
WRITE(6,*) 'of subintervals '
WRITE(6,*) ' '
READ(5,*) N


WRITE(*,6)
6 FORMAT(12X,'t(i)',11X,'w1(i)',11X,'w2(i)')

H=(B-A)/N
T=A


! the initiaal conditions
W1=ALPHA1
W2=ALPHA2

WRITE(*,1) T,W1,W2

!RK PARAMETER EVALUATIONS HERE

DO 110 I=1,N

X11=H*F1(T,W1,W2)
X12=H*F2(T,W1,W2)

X21=H*F1(T+H/2,W1+X11/2,W2+X12/2)
X22=H*F2(T+H/2,W1+X11/2,W2+X12/2)

X31=H*F1(T+H/2,W1+X21/2,W2+X22/2)
X32=H*F2(T+H/2,W1+X21/2,W2+X22/2)

X41=H*F1(T+H,W1+X31,W2+X32)
X42=H*F2(T+H,W1+X31,W2+X32)

W1=W1+(X11+2*X21+2*X31+X41)/6
W2=W2+(X12+2*X22+2*X32+X42)/6

T=A+I*H

WRITE(*,1) T,W1,W2
110 CONTINUE


STOP
1 FORMAT(3(1X,E15.8))
END