I have the code below :

- (id) initWithGame:(mainGame*)game {

    if ((self = [super init])) {

        isTouchEnabled_ = YES;
        self.game = game;

        CGSize size = [[CCDirector sharedDirector] winSize];
        screenH = size.height;
        screenW = size.width;

        character = [CCSprite spriteWithFile:@"o.png"];
        character.position = ccp( size.width /2 , size.height/2 );
        character.contentSize = CGSizeMake(72, 79);
        [self addChild:character z:10 tag:1];

        _body = NULL;
        _radius = 14.0f;


        // Create ball body and shape
        b2BodyDef ballBodyDef;
        ballBodyDef.type = b2_dynamicBody;
        ballBodyDef.position.Set(100/PTM_RATIO, 100/PTM_RATIO);
        ballBodyDef.userData = character;
        _body = _game.world->CreateBody(&ballBodyDef);

        b2CircleShape circle;
        circle.m_radius = 26.0/PTM_RATIO;

        b2FixtureDef ballShapeDef;
        ballShapeDef.shape = &circle;
        ballShapeDef.density = 1.0f;
        ballShapeDef.friction = 0.2f;
        ballShapeDef.restitution = 0.8f;
        _body->CreateFixture(&ballShapeDef);

        [self schedule:@selector(gameChecker:)];
        [self schedule:@selector(tick:)];

    }
    return self;
}


- (void)gameChecker:(ccTime) dt{

    if(character.position.y > 200){
        [self unschedule:@selector(tick:)];
        [self schedule:@selector(dropObject:)];

    }
}

- (void)tick:(ccTime) dt {

    b2Vec2 force;
    force.Set(_body->GetLinearVelocity().x, _body->GetLinearVelocity().y+1.0f);

    for (b2Body* b = _game.world->GetBodyList(); b; b = b->GetNext())
    {
        if (b->GetUserData() == character)
        {
            b->SetLinearVelocity(force);
        }
    }
    _game.world->Step(dt, 10, 10);
    for(b2Body *b = _game.world->GetBodyList(); b; b=b->GetNext()) {    
        if (b->GetUserData() != NULL) {
            CCSprite *ballData = (CCSprite *)b->GetUserData();
            ballData.position = ccp(b->GetPosition().x * PTM_RATIO,
                                    b->GetPosition().y * PTM_RATIO);
            ballData.rotation = -1 * CC_RADIANS_TO_DEGREES(b->GetAngle());
        }        
    }


}

-(void)dropObject:(ccTime) dt{
    b2Vec2 force;
    force.Set(_body->GetLinearVelocity().x, _body->GetLinearVelocity().y-1.0f);

    for (b2Body* b = _game.world->GetBodyList(); b; b = b->GetNext())
    {
        if (b->GetUserData() == character)
        {
            b->SetLinearVelocity(force);
        }
    }
    _game.world->Step(dt, 10, 10);
    for(b2Body *b = _game.world->GetBodyList(); b; b=b->GetNext()) {    
        if (b->GetUserData() != NULL) {
            CCSprite *ballData = (CCSprite *)b->GetUserData();
            ballData.position = ccp(b->GetPosition().x * PTM_RATIO,
                                    b->GetPosition().y * PTM_RATIO);
            ballData.rotation = -1 * CC_RADIANS_TO_DEGREES(b->GetAngle());
        }        
    }
}

I have been trying to get the effect that fruit ninja has when shooting the fruits. but it seems like its hard to get such animation so I was wondering if anyone can point me to the right direction and/or give me a sample code for a single object that gets thrown into the screen with a direction.