Question

a car having a mass of 1000kg is moving with a speed of 25 m/s applied brake and came to rest in 6 seconds.Which theorem can be used to find the work done to stop the car?

Answer 1

Given :

Mass of the car = 1000kg

Initial velocity = 25 m/s

Final velocity = zero

To Find :

Work done to stop the car.

Solution :

In this case work - kinetic energy theorem can be used to calculate work done to stop the car.

It states that work done is always equal to the change in kinetic energy.

$:\implies\:\underline{\boxed{\bf{\purple{W=\Delta KE=\dfrac{1}{2}m(v^2-u^2)}}}}$

» m denotes mass

» v denoted final velocity

» u denotes initial velocity

By substituting the given values;

$\sf:\implies\:W=\dfrac{1}{2}m(v^2-u^2)$

$\sf:\implies\:W=\dfrac{1}{2}\times1000(0^2-25^2)$

$\sf:\implies\:W=500\times(0-625)$

$\sf:\implies\:W=500\times(-375)$

$\sf:\implies\:\underline{\boxed{\bf{\orange{W=-187500\:J=-187.5\:kJ}}}}$

[Negative sign shows that force is acting in the opposite direction.]

Answer 2

$\huge\underline\blue{Answer}$:

⭐Given,

ㅤㅤFinal velocity, v=0

ㅤㅤInitial velocity, u=30ms^−1

☄️Force = mass x acceleration

ㅤㅤ[ F=ma ]

ㅤㅤㅤa=F/m=−5000/1000=−5ms^−2

⭐From the First equation of motion,

ㅤㅤㅤㅤㅤv=u+at

ㅤㅤㅤㅤㅤ0=30+(−5t)

ㅤㅤㅤㅤㅤ0=30−5t

ㅤㅤㅤㅤㅤ5t=30

ㅤㅤㅤㅤㅤt=30/5

ㅤㅤㅤㅤㅤt=6

☄️Hence, after6sec car will stop.

ㅤㅤㅤㅤㅤ❤Thank you❤