Question

give one example each of the type of motion when acceleration is positive

Answer 1

Originally Answered: What are the examples of positive acceleration?

Example 1: the simplest case: kick a football. The ball accelerates positively during the very short time that your foot is in contact with the ball. [Same with hitting a golf ball with a golf club.]

Example 2: a rocket is on the launch pad. At the end of the countdown, it accelerates upwards (probably at 6 g). positive acceleration.

Example 3: a more complicated case: free fall: the velocity is negative, pointing downwards. But the speed is increasing, so there is an acceleration. The acceleration is negativebecause it too, is downwards. A negative acceleration that increases the speed of a negative velocity, can be considered, (and actually is) positive.

Example 4: and even more complicated case: place the car’s transmission in reverse. Step on the gas. The car is increasing in speed so it is accelerating. This acceleration is negative because relative to the car, it is in reverse. The velocity is negative, because the car is in reverse. Again we have, a negative velocity increasing negatively. Positive acceleration.

Answer 2

In Example C, the object is moving in the positivedirection (i.e., has a positive velocity) and is slowing down. According to our principle, when an object is slowing down, the acceleration is in the opposite direction as the velocity. Thus, this object has a negative acceleration.