Question

If a car takes 5 s to reach a speed of 72 kmph then the magnitude of its average acceleration is​

Answer 1

Given :

⟶ Initial speed of car = zero

⟶ Final speed of car = 72kmph

⟶ Time interval = 5s

To Find :

➾ Acceleration of car.

Concept :

⟹ Acceleration is defined as the rate of change in speed of moving body.

⟹ It is a vector quantity having both magnitude as well as direction.

⟹ It can be positive, negative or zero.

⟹ SI unit : m/s²

✴ First equation of kinematics :

• v = u + at

፨ v denotes final speed

፨ u denotes initial speed

፨ a denotes acceleration

፨ t denotes time

Conversion :

➳ 1kmph = 5/18mps

➳ 72kmph = 72 × 5/18 = 20mps

Calculation :

⇒ v = u + at

⇒ 20 = 0 + a(5)

⇒ a = 20/5

⇒ a = 4m/s²

Answer 2

Given:-

Initial velocity = 0 m/s

final velocity = 72 kmph = 72 × 5/18 = 20 mps

Time taken = 5s

To Find:-

The acceleration

Concept:

In non uniform motion velocity varies with time. The changing the velocity of an object per unit time is measured by the physical quantity is called acceleration. It is the rate of increase of velocity of a body with respect to time.

Formula used:-

Here Formula of kinematics is used

Where,

v= final velocity

u = initial velocity

t = Time taken

a = acceleration

Calculation:-

➞ v = u+ at

➞ 20= 0 + a× 5

➞20 =0 + 5a

➞20= 5a

➞ a = 20/5

➞ a = 4 m/s^2