Question

a truck moving with a velocity of 65 km/hr comes to rest after applying brakes in 8 seconds what is retardation of the truck​

Answer 1

Answer :

Here, we are given the initial velocity of the truck and the time taken by the truck to come to rest. And we need to calculate the retardation of the truck. For that, firstly we will convert the initial velocity of the truck from km/h into m/s. And then by using the first equation of motion we will find the acceleration, consequently we will find the retardation of the truck.

Solution :

Given :

• Initial velocity of the truck = 65 km/h
• Final velocity of the truck = 0 m/s [Because it comes to rest.]
• Time taken by the truck to come to rest = 8 seconds

To find :

• Retardation of the truck

Required Solution :

To convert the initial velocity of the truck from km/h into m/s. Multiply the value by 5/18.

⇒ Initial velocity = 65 × 5/18

⇒ Initial velocity = 325/18

⇒ Initial velocity = 18.05

The initial velocity of the truck = 18.05 m/s or 325/18 m/s

Using the first equation of motion,

• v = u + at

where,

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

we have,

• v = 0 m/s
• u = 18.05 m/s or 325/18
• t = 8 seconds

Substituting the given values :

⇒ 0 = 325/18 + a × 8

⇒ - 325/18 = 8a

⇒ - 325/18 × 1/8 = a

⇒ - 325/144 = a

⇒ - 2.26 = a

Acceleration of the truck = - 2.26 m/s²

Negative acceleration is known as retardation.

⇒ Retardation = 2.26 m/s²

Therefore, the retardation of the truck = 2.26 m/s²