Question

What is the acceleration of a race car that moves at constant velocity of 300 km/hr?
(A) 73.32 \[m/{\sec ^2}\]
(B) 0 \[m/{\sec ^2}\]
(C) 63.33 \[m/{\sec ^2}\]
(D) 53.33 \[m/{\sec ^2}\]

Answer 1

Hint It is given that velocity of the car is 300km/hr. Convert km/hr to m/s units and use laws of motion equations to identify the correct acceleration value.

Complete step by step solution
Given that race car moves at a constant velocity of 300 km/hr. Now converting this to m/s
We get the value as ,
V=\[300 \times \dfrac{5}{{18}}\]= 83.33 m/s
Now, it is stated that the car is constantly moving with a velocity of 83.33m/s. However, by definition of acceleration, it is the change in velocity with respect to time that causes acceleration of a body. Therefore, In question there has been no mention of initial velocity or state of rest.
So when the car moves in a constant velocity, the acceleration of the given body will also be constant, which is equal to zero.
To substantiate this , we use a simple equation of motion,
Which is \[v = u + at\]
Now, \[v - u = at\]
We are unaware about the starting point of the body. Therefore, since the velocity is mentioned as constant the initial velocity u will be equal to final velocity v.
Hence,
\[\dfrac{{300 - 300}}{t} = a\]
Which implies that a=0

Therefore, Option (b) is the right answer for the given question.

Note
Velocity of an object is defined as the change of body’s position with respect to a reference point or frame or plane with respect to time. Velocity is a vector quantity as it measures change in one quantity with respect to another. Velocity is measured in meters per seconds as per the S.I unit framework.
Acceleration is defined as the rate of change of velocity per unit time. Like velocity, Acceleration is also a vector quantity.