Question

When a car driver travelling at a speed of 10 m/s applies brakes and brings the car to rest in 20 s, then the retardation will be
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Answer 1

Answer:

• Retadartion of the car = 0.5 m/s²

Explanation:

Given

• A car is travelling at a speed = initial velocity of Car, u = 10 m/s

• Brakes are applied to bring the car to rest, so the final velocity of Car, v = 0
• time taken to bring the car to rest after applying brakes, t = 20 s

To find

• Retardation of the Car =?

Formula required

• First equation of motion

       v = u + a t

Where

v = final velocity

u = initial velocity

a = acceleration

t = time taken

Solution

Let, acceleration of car be a

Using the first equation of motion

→ v = u + a t

→ 0 = 10 + a × 20

→ - 10 = 20  a

→ a = -10 / 20

→ a = -0.5  m/s²

Therefore, acceleration of the car is -0.5 m/s². and hence

• Retardation of the car is 0.5 m/s².

Answer 2

Question :-

When a car driver travelling at a speed of 10 m/s applies brakes and brings the car to rest in 20 s, the retardation will be

Given :-

• u = 10 m/s
• v = 0 m/s
• t = 20 s

To find :-

Retardation

Solution :-

Substituting the values in 1st equation of motion :-

v = u + at

0 = 20 + 20a

20a = -20

a = -1 m/s²

Retardation = 1 m/s²