University Physics with Modern Physics

Wolfgang Bauer, Gary D. Westfall

ISBN #9780072857368

1st Edition

3,117 Questions

54,786 Students Helped

Homework Questions

Summary

Learning Objectives

Key Concepts

Example Problems

Explanations

Common Mistakes

Summary

This section emphasizes the central role of energy in physical processes and introduces the key concepts of kinetic energy, work, and power. It illustrates how work can be viewed as the transfer of energy by a force acting over a displacement, including the use of the scalar product. The work–kinetic energy theorem bridges the gap between force and energy analysis, allowing for alternative approaches to solving problems normally tackled via Newton’s laws. Additionally, concepts such as Hooke’s Law for springs demonstrate how energy storage and conversion work in elastic systems. Mastery of these ideas equips learners to analyze a wide range of mechanical and physical phenomena.

Learning Objectives

Key Concepts

CONCEPT

DEFINITION

Definition: The study of the structure and behavior of atoms, from the early Bohr model to the complete quantum mechanical treatment of the hydrogen atom and multi?electron systems.

The study of the structure and behavior of atoms, from the early Bohr model to the complete quantum mechanical treatment of the hydrogen atom and multi?electron systems. •

Example Problems

Example 1

Which of the following is a correct unit of energy? a) $\mathrm{kg} \mathrm{m} / \mathrm{s}^{2}$ c) $\mathrm{kg} \mathrm{m}^{2} / \mathrm{s}^{2}$ e) $\mathrm{kg}^{2} \mathrm{~m}^{2} / \mathrm{s}^{2}$ b) $\mathrm{kg} \mathrm{m}^{2} / \mathrm{s}$ d) $\mathrm{kg}^{2} \mathrm{~m} / \mathrm{s}^{2}$

Example 2

An $800-\mathrm{N}$ box is pushed up an inclined plane that is $4.0 \mathrm{~m}$ long. It requires $3200 \mathrm{~J}$ of work to get the box to the top of the plane, which is $2.0 \mathrm{~m}$ above the base. What is the magnitude of the average friction force on the box? (Assume the box starts at rest and ends at rest.) a) $0 \mathrm{~N}$ c) greater than $400 \mathrm{~N}$ b) not zero but d) $400 \mathrm{~N}$ less than $400 \mathrm{~N}$ e) $800 \mathrm{~N}$

Example 3

An engine pumps water continuously through a hose. If the speed with which the water passes through the hose nozzle is $v$ and if $k$ is the mass per unit length of the water jet as it leaves the nozzle, what is the kinetic energy being imparted to the water? a) $\frac{1}{2} k v^{3}$ c) $\frac{1}{2} k v$ e) $\frac{1}{2} v^{3} / k$ b) $\frac{1}{2} k v^{2}$ d) $\frac{1}{2} v^{2} / k$

Example 4

A $1500-\mathrm{kg}$ car accelerates from 0 to $25 \mathrm{~m} / \mathrm{s}$ in $7.0 \mathrm{~s}$ What is the average power delivered by the engine $(1 \mathrm{hp}=746 \mathrm{~W}) ?$ a) $60 \mathrm{hp}$ c) $80 \mathrm{hp}$ e) $180 \mathrm{hp}$ b) $70 \mathrm{hp}$ d) $90 \mathrm{hp}$

Example 5

Which of the following is a correct unit of power? a) $\mathrm{kg} \mathrm{m} / \mathrm{s}^{2}$ c) J e) $W$ b) $N$ d) $\mathrm{m} / \mathrm{s}^{2}$