title: How to implement trolley-like physics behaviour in Unity
body: <p>I am stuck with two things while trying to simulate the physics setup for a trolley-like object (push powered vehicle with free rotating wheels on the front and fixed wheels on the back).</p>
  
  <p>I have the <code>RigidBody</code> with its mesh and four <code>WheelColliders</code>, the object moves fine if I just apply torque to the wheels. However if I use the <code>AddForce</code> method on the <code>RigidBody</code> it won't move; I see the object being pushed (slightly balancing) but the wheels won't rotate so it stays in place. How can I get the wheels to move if the object is being pushed?</p>
  
  <p>My other problem is to simulate the standard 360 degrees rotating wheels on the front of the trolley. What would be the best way to simulate this? I was thinking about a horizontal <code>WheelCollider</code> and a vertical one as a child but that seems really weird and I doubt it will actually work. Any ideas?</p>