def model_y(ec, params):
    """
    Simple model of a kinematic trajectory.

    Args:
        ec (`dict`): dictionary with a key 't' leading to a float value
        params (`dict`): dictionary with keys 'v0' and 'g' leading to float values

    Returns:
        float: y-value at the given time assuming the given parameters
    """
    # read in the inputs
    t = ec['t']
    v0 = params['v0']
    g = params['g']

    # compute and return
    return v0*t - 0.5 * g * t**2