Question

a car moving with the speed of 72 km per HR after applying brakes it needs 5 seconds to stop calculate the the force applied by brakes​

Answer 1

Correct Question:-

a car of mass 1000kg moving with the speed of 72 km per HR after applying brakes it needs 5 seconds to stop calculate the the force applied by brakes

Given:-

• Initial velocity ,u = 72km/h

•Final velocity ,v = 0m/s

• Time taken ,t = 5s

• Mass ,m = 1000kg

To Find :-

• Force F

Solution:-

Conversion of Unit

72×5/18 = 20m/s

Firstly we calculate the acceleration of the car

→ a = v-u/t

Substitute the value we get

→ a = 0-20/5

→ a = -20/5

→ a = -4m/s²

here , negative sign show retardation .

Now Calculating the Force

→ F = m×a

Substitute the value we get

→ F = 1000×4

→ F = 4000N

Therefore , 4000N Force required to stop the car.

Answer 2

$\huge{\underline{\underline{\green{\sf \ast Correct \: Question}}}}$

A car moving with the speed of 72 km/h after applying brakes it needs 5 seconds to stop calculate the the force applied by brakes. The mass of the care is 100kg

____________________

$\underline{\underline{\pink{\sf \ast Given:}}}$

• Initial Velocity, u = 72km/h
• Final Velocity, v = 0m/s
• Time, t = 5sec
• Mass of Car, m = 100kg

$\underline{\underline{\pink{\sf \ast Find:}}}$

• Force exerted by brakes on the Car.

$\underline{\underline{\pink{\sf \ast Solution:}}}$

F1stly convert Initial velocity from km/h to m/s

So,

$\sf \to 72 \times \dfrac{5}{18} = \dfrac{360}{18}$

$\sf \to \cancel{\dfrac{360}{18}} = 20m/s$

So, u = 20 m/s

____________________

By using 1eq. of Motion

$\boxed{\dag\boxed{\sf v = u + at} \dag}$

$\sf\to v - u = at$

$\sf\to a = \dfrac{v - u}{t}$

Now, putting the given values in this we, get

$\sf\to a = \dfrac{0 - 20}{5}$

$\sf\to a = \dfrac{-20}{5}$

$\sf\to a = -4{m/s}^{2}$

____________________

Now, we know that

$\boxed{\dag\boxed{\sf F = ma} \dag}$

Now, put the values in this we, get

$\sf \to F = 100 \times 4$

$\sf \to F = 400 N$

$\therefore$ 400N of force required to stop the car of mass 100kg