I attached a diagram, according to the description given, to better understand the problem. The car accelerates, at a 'a' speed, which will also experience the hanging object, in two components:
The one in x, with 'a' in the opposite direction to the car's address
The one found in y, the product of gravity. The two components are related through the tangent and the respective angle, as well,
To identify, we know that it can be expressed as a function of speed,
Replacing in our angle formula,
If there is no friction, we consider the vertical forces of both the Washes and the Normal car. So,
Therefore the relationship with the vertical component would be given by,
