AngularJS getting JSON data from array2 in array1

I have JSON like this

{
    "cars":[
        {
            "id":"012",
            "model":"honda",
            "parts":[
                {
                    "id":"p1",
                    "name":"tyre",
                },
                {
                    "id":"p2",
                    "name":"muffler",
                }
            ]
        },
        {
            "id":"022",
            "model":"vw",
            "parts":[

            ]
        }
    ]
}

I am new to AngularJS and I have 2 dropdowns, dropdown1 showing car models like:

DROPDOWN1
honda
vw

and dropdown 2 that is supposed to be loaded with parts for selected car model in dropdown1. For example, if I select "honda" in dropdown1, dropdown2 should be loaded with:

DROPDOWN2
tyre
muffler

If I select "vw" in dropdown1, then dropdown2 will not load since there are no parts for VW.

I have html with 2 select (dropdowns) like this, note that I am using ng-options rather than repeat:

<p><strong>Select a car</strong></p>
<select 
    required
    ng-change="selectCarAction()"
    ng-model="selectCar" 
    ng-options="car.model for car in cars track by car.id">
  <option value="" label="Select a car"></option>  
</select>

<p><strong>Select a part</strong></p>
<select 
    required
    ng-model="selectPart" 
    ng-options="part.name for partin car.part track by part.id">
  <option value="" label="Select a part"></option>  
</select>

And in my js file, I get my car response data like:

      $scope.myData= JSON.stringify(myresponse.data);
      $scope.cars= myData.data.cars; 

, then I have function to get selected car and the intention is to also load dropdown2 once I get selected car:

$scope.selectCarAction = function(){
  if ($scope.selectCar == null){
    console.log("You selected car: N/A");
  } else {
    console.log("You selected car: " + $scope.selectCar.model);
    $scope.parts= $scope.selectCar.parts;

    // How do I load these parts in DROPDOWN2 above?

  }
};

While my DROPDOWN1 loads fine, my DROPDOWN2 is never loaded but in the js function above, my $scope.parts gets the parts. How do I load these into my DROPDOWN2?