Question

An acceleration will be observed by the object if:
A. it slows down
B. it changes direction.
C.it speeds up
D. it comes to a stop.
E. all of these.

Answer 1

Acceleration is rate of change of velocity with respect to time. Also, velocity is the rate of change of displacement with respect to time. So, we can say that acceleration depends on the velocity. so when velocity varies with displacement then, the corresponding acceleration also varies.

Complete answer:
Acceleration is the rate at which an object changes its velocity. According to Newton's 2nd law of motion, when a constant force acts on a body it causes it to accelerate with changing velocity.
Acceleration depends on the velocity vector. It is a vector quantity as it has both magnitude and direction. Velocity is also a vector quantity, as it is the rate of change of displacement per unit time. Displacement is different from the distance, as displacement is a vector quantity and it has both direction and magnitude. But the distance has only magnitude value.
When the object slows down, the acceleration is in the opposite direction, and the object will have negative acceleration. Also, when velocity decreases, the acceleration is constant.
Acceleration depends on the motion of the object moving from one position to another. A body can have zero velocity and still accelerate. This is possible when there is constant velocity, without changing direction.
Also, when the object speeds up, velocity changes and then acceleration also changes.
When the object comes to a stop, the acceleration does not seem to be zero. For this we will discuss the motion of a projectile, In which the object reaches to the maximum height then at this point velocity is zero, but the object is under the effect of gravity. So, the particle has zero velocity but still acceleration is there. Also, acceleration is the ratio of change in velocity to the change in time intervals.
Therefore, the acceleration is observed in all the options given in question.

Hence, we conclude that the option E is correct.

Note:
Acceleration is the rate of change of velocity with respect to time. Acceleration depends upon the velocity attained by the object to be in motion. Velocity is the rate of change of displacement per unit time. Acceleration depends upon the nature of velocity.