Download the .fla file carRotatingWheels.fla by right-clicking and saving or left mouse button clicking and opening it in Flash. 

carGo_btn.addEventListener(MouseEvent.CLICK, carGo);
carStop_btn.addEventListener(MouseEvent.CLICK, carStop);

wheelsGo_btn.addEventListener(MouseEvent.CLICK, wheelsGo);
wheelsStop_btn.addEventListener(MouseEvent.CLICK, wheelsStop);

function carGo(evt:MouseEvent) {
    play();
}

function carStop(evt:MouseEvent) {
    stop();
}

// 
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wheelsGo_btn.addEventListener(MouseEvent.CLICK, wheelsGo);
wheelsStop_btn.addEventListener(MouseEvent.CLICK, wheelsStop);

function wheelsGo(evt:MouseEvent) {
    theCar.rearWheel.play();
    theCar.frontWheel.play();
}

function wheelsStop(evt:MouseEvent) {
    theCar.rearWheel.stop();
    theCar.frontWheel.stop();
}