The velocity of a car teduces from 30 km/h as the car approaches a stop sigh. Is this an example of positive or negative accelerationthe

The stopping car has negative acceleration.

Explanation:

We know acceleration is the rate of change of velocity. That is

Acceleration (a) = (Final velocity - Initial velocity) / Time taken.

Here Final velocity = 0 km/h (car stops) and initial velocity = 30 km/h

So acceleration = (0-30) / time = - 30 / time

Time is always positive, so - 30/time is negative, so the stopping car has negative acceleration.