Trying to get accelerated jump speed.

Well, you are missing a lot of info for anyone to help you. No deceleration so idk what type you dealing with.

You can use my own code which is in Boo, very easy to transfer to unityscript. Keep in mind "single" means float. It is also assuming 2D physics which 'w' and 'spacebar' are defined as jump inputs.

 import UnityEngine
 
 [AddComponentMenu("Character/TwoDPlatformController")]
 [RequireComponent( CharacterController )]
 
 class TwoDPlatformController ( MonoBehaviour ): 
     //public     test  = TwoDPlatformControllerJumping()  Access another class will also appear in inspector
     public walkSpeed   as single     = 6.0F
     public runSpeed       as single     = 10.0F
     public jumpSpeed   as single     = 8.0F
     public gravity     as single     = 20.0F
     public doubleJumpEnabled  as bool= true
     public extraJump as int          = 1
     public autoRotate  as bool       = true
     public maxRotationSpeed as single = 360
     
     private moveDirection as Vector3 = Vector3.zero
     private curNumJump    as int     = 0
     private curSpeed      as single  = 0.0F
     
     internal jumped       as bool    = false
     
     private jumpingApexReached as bool = false
     
     private controller as CharacterController
 
     
     def Update():
         PlayerMovement()
         HandleEvents()
         
         
     def PlayerMovement ():
         controller = GetComponent(CharacterController)
         
         // While character is grounded allow to jump and horizontal movement
         // Player is restricted in jump movement.  One way jump if double jump disabled
         if controller.isGrounded:
             curNumJump = 0
             jumped = false
             
             // Assign run speed when pressing left ctrl
             if Input.GetKey(KeyCode.LeftControl):
                 curSpeed = runSpeed
                 
             // Assign default walk speed
             else:
                 curSpeed = walkSpeed
                 
             // Apply vector direction, only focusing on X- axis
             moveDirection = Vector3( Input.GetAxis('Horizontal') * curSpeed, 0, 0 )
             
             // If player has jumped
             // Allow player to single jump while in air
             // Check if player has reached jump apex, used for animation states
             if hasSingleJumped():
                 SingleJump()
                 hasReachedJumpingApex()
         
         // Player is in the air
         // Allow the player the option of extra jumping, already checks if extra jumping is enabled
         // Check if player has reached jump apex, used for animation states
         // TODO: Future implementation, allow user to shoot while in air
         else:
             if hasExtraJumped():
                 ExtraJump()
                 hasReachedJumpingApex()
             
         
         ApplyGravityForce()
 
         // Apply new vector direction to the character controller
         controller.Move( moveDirection * Time.deltaTime )
         
     def SingleJump ():
     // Immediately present number of allowed mid air jumps when landed
     // Allow player to jump
         moveDirection.y = jumpSpeed
         jumped = true
             
     def ExtraJump ():
     // Allow player the capability to jump multiple times in mid air
     //  Number of times is based on 'extraJump'
     //  Once limit is reach player must land before jumping again
     // When jumping horizontal movement is unlocked for that jump then it will be locked again
     
         if curNumJump < extraJump:
             moveDirection = Vector3( Input.GetAxis('Horizontal') * walkSpeed, 0, 0 )
             moveDirection.y = jumpSpeed
             curNumJump += 1    
             
     def ApplyGravityForce ():
         moveDirection.y -= ( gravity * Time.deltaTime )
         
     def HandleEvents ():
     // Events taken place are of action types: shooting, special attacks, interactable object, etc
         pass
         
     def hasSingleJumped ():
         return ( Input.GetButtonDown( 'Jump' ) or Input.GetKeyDown( 'w' ) ) 
         
     def hasExtraJumped  ():
         return ( Input.GetButtonDown( 'Jump' ) or Input.GetKeyDown( 'w' )  and doubleJumpEnabled )
         
     def hasReachedJumpingApex ():
         if jumped and controller.velocity.y <= 0.0:
             jumpingApexReached = true
             return jumpingApexReached
         
         else:
             if controller.isGrounded:
                 jumpingApexReached = false
                 return jumpingApexReached
         
     def getSpeed ():
         return moveDirection.x

You can remove AddComponentMenu part. Change [RequireComponent..] to @script RequireComponent(..)

This uses the CharacterControllr provide by Unity which is a way of control the player without the interruption of physics to provide unique movements.