Question

A car increases its speed from 39 km/hr to 75 km/hr in 10 seconds. Its acceleration is a) 3 m/s2 b) 0.8 m/s 2 c) 1 m/s2 d) 8 m/s2

Answer 1

Given :

Initial velocity of the car = 39 km/hr

final velocity of the car = 75km/hr

Time taken = 10 sec

To find :

The acceleration of the car

Solution :

Firstly we have to convert km/hr to m/s

we know that,

» 1km/hr = 5/18km/hr

» 39km/hr = 39 × 5/18 = 10.8 m/s

» 75km/hr = 75 × 5/18 = 20.8 m/s

Accerlation is the rate of change of velocity.

• It is a vector quantity having both magnitude as well as direction.
• SI unit of acceleration is metre per second square.

As we are provided with initial velocity, final velocity and time we can use first equation of kinematics that is,

v = u + at

• v denotes final velocity
• u denotes initial velocity
• a denotes acceleration
• t denotes time taken

by substituting all the given values in the formula,

➝ v = u + at

➝ 20.8 = 10.8 + a(10)

➝ 20.8 - 10.8 = 10a

➝ a = 10/10

➝ a = 1m/s²

Thus, the acceleration of the car is 1m/s².

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