Question

How can acceleration be negative?

Answer 1

Hint: In this question, we will first see the basic definition of acceleration. This will help us to answer our question easily. Also, we will see the difference between positive and negative acceleration. Also, we will study the basic difference between speed and velocity, for our better understanding.

Complete answer:
As we know, the acceleration ‘a’ is defined as the rate of change in velocity of an object. The acceleration is measured in meters per Second Square. Also, acceleration has both magnitude and direction. So, we can say that acceleration is a vector quantity.
Now, the direction of the acceleration depends on two things:
If the object is speeding up or the object is slowing down
If the object is moving in the positive or negative direction.
Now, we will see the general principle that will help us to determine the acceleration:
According to this principle ‘If an object or body is slowing down, then its acceleration is in the opposite direction of its motion’.
So, we can say that when an object is speeding up, here the acceleration is in the same direction as the velocity of the object or body. Thus, the object has a positive acceleration.
Also, when we say that an object is moving in the negative direction or it has a negative velocity and is slowing down that means the object is slowing down, the acceleration of the object or body is in the opposite direction as the velocity. So, the object or body has negative acceleration.
Therefore, we get the required answer to our question.

Additional information:
As we know the basic difference between speed and velocity i.e., speeds is the measure of how fast an object can travel, whereas velocity gives us the direction of speed. Speed is a scalar quantity which means it has only magnitude, whereas velocity is a vector quantity which means velocity has both magnitude and direction. The S.I unit of velocity is meter per second represented by m/sec.

Note:
We should remember that any physical quantity can be a scalar or vector. We can answer this question easily by knowing the basic definition of acceleration. We should also know that, if velocity of an object is constant then the value of acceleration will be zero.