Answer:
A car that increases its speed from 20 km/h to 100 km/h undergoes positive acceleration.
In fact, acceleration is defined as:
where v is the final velocity, u is the initial velocity, and t is the time taken. t has always positive sign, and in this case, the final velocity (v=100 km/h) is greater than the initial velocity (u=20 km/h), so the numerator is positive and therefore the acceleration is positive.
Explanation:
