Question

Which of these is an example of deceleration?
A. a roller coaster moving down a steep hill
B. an airplane following a straight flight path
C. a bird taking off for flight
D. a car approaching a red light

Answer 1

In order to solve this question, we should know about deceleration. When a body’s velocity is decreasing then the magnitude of acceleration which is the rate of change of velocity is negative and this negative acceleration is termed as deceleration.Here, we will discuss each option one by one and will figure out which option is an example of deceleration.

Complete answer:
Considering option (A) a roller coaster moving down a steep hill. So, when a roller coaster comes downwards on a steep hill it may either have an increase in its velocity or decrease so, it’s not a perfect example of deceleration.

Considering option (B) an airplane following a straight flight path. When an airplane has to take flight it must increase its velocity and thus have a positive acceleration, so it’s also not an example of deceleration.

Considering option (C) a bird taking off for flight. When a bird needs to fly, it applies force through their wings and increases in velocity to move ahead resulting in positive acceleration, so it’s also not an example of deceleration.

Considering option (D) a car approaching a red light. So, when a car approaches a red signal light it must have to become at rest before the signal so it must have decreased in its velocity and decreasing in velocity results in negative acceleration which is called deceleration. So, it’s an example of deceleration.

Hence, the correct option is (D).

Note: It should be remembered that, deceleration is just the term used for indicating body has negative acceleration which shows body is decreasing its velocity with time, and deceleration has all the properties similar to acceleration like its SI unit, dimensions and it’s a vector quantity.