Physics 208-02 – Introductory Physics II

Solution Set 2

Nazareth College

Department of Chemistry & Biochemistry

Robert F Szalapski, PhD – Adjunct Lecturer

www.CallMeDrRob.com

Spring 2012

## § Chapter 14, Problem 5

A water heater can generate . How much water can it heat from to per hour.

In one hour the amount of heat available will be

We will equate this to the heat required to warm a mass or water as

I have expressed the answer to only two significant figures, but note that the author expressed to only one significant figure so actually we should round one more place.

## § Chapter 14, Problem 6

A small immersion heater is rated at . Estimate how long it will take to heat a cup of soup (assuming it is of water) from to .

Let’s begin by calculating the required heat.

We now calculate the time using

## § Chapter 14, Problem 11

A glass thermometer reads before it is placed in of water. When the water and the thermometer come to equilibrium, the thermometer reads . What was the original temperature of the water.

Heat is flowing from the water into the glass thermometer. The sum of the two heats will total zero.

## § Chapter 14, Problem 12

What will be the equilibrium temperature when a block of copper at is placed in a aluminum calorimeter cup containing of water at ?

In this case we have three terms to include with heat flowing from the copper into the water and aluminum.

## § Chapter 14, Problem 15

How long does it take a coffee pot to bring to a boil of water initially at ? Assume that the part of the pot that is heated with the water is made of of aluminum and that no water boils away.

First compute the heat required.

We now calculate the time using

## § Chapter 14, Problem 18

The head of a hammer has a speed of just before it strikes a nail and is brought to rest. Estimate the temperature rise of a iron nail generated by 10 such hammer blows done in quick succession. Assume the nail absorbs all the energy.

The kinetic energy of the hammer is

The assumption is that this amount of kinetic energy is transfered to the nail ten (10) times in quick succession. If all of this goes into heating the nail, then

## § Chapter 14, Problem 21

How much heat is needed to melt of silver that is initially at ?

We need to include the heat to first elevate the temperature of the silver to its melting point of and add the amount of heat for the phase transition.

## § Chapter 14, Problem 25

A cube of ice is taken from the freezer at and placed in a aluminum calorimeter filled with of water at room temperature of . The final situation is observed to be all water at . What was the mass of the ice cube?

This ice must first warm to its melting point, it must then go through the phase transition, and then the resulting liquid must warm to the final temperature. The original water plus the aluminum calorimeter must both cool to the final temperature. That’s a total of five terms!

## § Chapter 14, Problem 28

What mass of steam at must be added to of ice at to yield liquid water at ?

This problem will have four terms. The steam must condense, and the resulting water must cool. The ice must melt, and the resulting water must warm.

## § Chapter 14, Problem 30

A bullet traveling at penetrates a block of ice at and comes to rest within the ice. Assuming that the temperature of the bullet doesn’t change appreciably, how much ice is melted as a result of the collision.

The idea is that the kinetic energy of the bullet is completely converted to heat which goes into melting ice.