(a) Explanation Given info: The mass of the car is 1500 kg , the mass of the brakes is 6.00 kg , the velocity of the before the brakes was applied 25.0 m / s , the initial temperature of the brakes is 20.0 ° C ., the internal energy of the system is transformed into the brakes whenever the car stops. The specific heat of the aluminum brakes is 900 J / kg ⋅ °C , the melting point for aluminum is 660 ° C . The formula to calculate the internal energy in brakes is E int = m b c Δ T Here, E int is the internal energy of the system. m b mass of the brakes. c is the specific heat of the aluminum brakes. Δ T is change in temperature. The change in the temperature is the (final melting temperature – the initial temperature) Therefore Δ T = 660°C − 20 .0°C Consider n be the number of times car stopped so n number of times the kinetic energy of the system was transferred in to the brakes. Thus calculate the value of n for which the n times the kinetic energy was stored in the internal energy of the system that is n times the kinetic energy is equal to internal energy n K = E int Here, K is the kinetic energy of the car. Substitute m b c Δ T for E int in equation (1) n K = m b c Δ T (1 The formula to calculate the kinetic energy of the car is K = 1 2 m c v 2 (2) Here, m c is the mass of the car v is the velocity of car (b) To determine The important aspect ignored in part (a) which will be considered in realistic approach.

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ISBN: 9780100460300

Author: SERWAY

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Question

Chapter 20, Problem 20.24P

(a)

To determine

The number of stops the car made before the brakes start to melt.

(b)

To determine

The important aspect ignored in part (a) which will be considered in realistic approach.

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Chapter 20 Solutions

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The number of stops the car made before the brakes start to melt.

Solution Summary: The author explains how the internal energy of the system is transformed into the brakes whenever the car stops.

Concept explainers

The number of stops the car made before the brakes start to melt.

The important aspect ignored in part (a) which will be considered in realistic approach.

Chapter 20 Solutions