Question

Eya !!

A car is moving in a straight line with speed 18km/h . It is stopped in 5 secs by applying the brakes . Find --

1) The speed of the car in m/s

2) retardation

3) the speed of car after 2 secs of applying the brakes.

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Answer 1

please check the attached file and every calculation is in m/s

Answer 2

Motion in a Straight Line :

Solution :

Given, Speed of car = 18 km/h

Time = 5 seconds

1 ). Speed of car in m/s

Speed of car in m/s = $\mathsf{18{\times{\dfrac{5}{18}}}}$

➡️ Speed of car in m/s = $\mathsf{5\:m{s} ^{-1}}$

2 ). Retardation :

Initial Velocity, u = 5 m/s

Final Velocity, v = 0 m/s

Using 1st equation of motion;

⚫ v = u + at

0 = 5 + a × 5

0 = 5 + 5a

-5a = 5

a = $\mathsf{\dfrac{-5}{5}}$

↪️ a = - 1

➡️ Retardation = $\mathsf{1\:m{s} ^{-2}}$

3. Speed of car after 2 seconds of applying breaks :

Given, Time, t = 2 seconds

To find : v =?

u = 5 m/s

Acceleration, a = $\mathsf{-1\:m{s} ^{-2}}$

Using 1st equation of motion :

v = u + at

v = 5 + ( - 1) (2)

v = 5 - 2 = 3

➡️ v = $\mathsf{3\:m{s} ^{-1}}$