# A 2000-kg car is traveling at 96.6 km/hr when it is braked to a stop. What is the maximum...

## Question:

A 2000-kg car is traveling at 96.6 km/hr when it is braked to a stop. What is the maximum possible thermal energy generated in the brakes?

## Conservation Law of Energy:

Consider a system in which some amount of energy is trapped. Here, we have assumed that the given system is perfectly isolated. In this case, the magnitude of the trapped energy will not change over time. This proves that the energy is s conserved quantity and it can neither be created nor it can be destroyed.

Given data:

• Mass of the car, {eq}m = 2000 \ kg {/eq}
• Initial speed, {eq}u = 96.6 \ km/h = 26.83 \ m/s {/eq}
• Final speed, {eq}v = 0 {/eq}

Assume all the energy generated during stopping of the car is changed into the thermal energy.

Here, the thermal energy produced in this case will be equal to the change in the kinetic energy.

{eq}\begin{align*} E &= \frac{1}{2}mu^{2} - \frac{1}{2}mv^{2}\\ E &= \frac{1}{2} \times 2000 \times (26.83)^{2} - \frac{1}{2} \times 2000 \times (0)^{2}\\ E &=719848.9 \ J.\\ \end{align*} {/eq}