### Unit 4: Dynamics

The study of motion is kinematics, which describes the way objects move, their velocity, and their acceleration. Dynamics consider the forces that affect the motion of moving objects. Newton's laws of motion are the foundation of dynamics. These laws provide examples of the breadth and simplicity of principles under which nature functions. They are also universal laws in that they apply to similar situations on Earth as well as in space.

**Completing this unit should take you approximately 26 hours.**

### 4.1: Newton's First and Second Laws of Motion

Please click on the link above and watch this lecture series, pausing to take notes, before moving on to the reading below.

Read sections 4.1, 4.2, and 4.3 of "Chapter 4: Dynamics: Force and Newton's Laws of Motion" (pages 123 to 132). Look over the corresponding conceptual questions on pages 155 and 156 to test your understanding of the sections.

Try solving these practice problems.

### 4.2: Newton's Third Law of Motion and Normal and Tension Forces

Watch this lecture series, pausing to take notes, before moving on to the reading below.

Read sections 4.4 and 4.5 of "Chapter 4: Dynamics: Force and Newton's Laws of Motion" (pages 132 to 142). Look over the corresponding conceptual questions on page 156 to test your understanding of the sections.

Try these practice problems, and be sure to make a serious attempt before viewing the answers.

### 4.3: Applications of Newton's Laws of Motion

Watch this lecture series, pausing to take notes, before moving on to the reading below.

Read sections 4.6 and 4.7 of "Chapter 4: Dynamics: Force and Newton's Laws of Motion" (pages 142 to 150). Look over the corresponding conceptual questions on page 156 to test your understanding of the sections.

Try solving these practice problems.

Work on solving problems 1 through 10 from SAC114. The solutions are available, but make a serious attempt to solve the problems before looking at the solutions.

### 4.4: Friction

Watch this lecture series, pausing to take notes, before moving on to the reading below.

Read section 5.1 of "Chapter 5: Further Applications of Newton's Laws: Friction, Drag, and Elasticity" (pages 163 to 169). Look over the corresponding conceptual questions on page 182 to test your understanding of the sections.

Try solving these practice problems.

Work on solving problem 3 from SAC102. The solution is available, but make a serious attempt to solve the problem before looking at the solution.

### 4.5: Springs

Watch this lecture series, pausing to take notes, before moving on to the reading below.

Read section 16.1 on Hooke's Law and motion and energy associated with a spring (pages 550 to 553). Look over the corresponding conceptual question on page 582 to test your understanding of the sections.

Try solving these practice problems.

Examine this demonstration. Note that the spring always exerts force in the direction that returns the spring to its original unstretched length.

Work on solving problems 1 and 2 from SAC102 and 1, 2, and 3 from SAC109. The solutions are available, but make a serious attempt to solve the problems before looking at the solutions.

### 4.6: The Simple Pendulum

Read section 16.4 on the simple pendulum (pages 559 to 561). Look over the corresponding conceptual question on page 582 to test your understanding of the sections.

Try solving these practice problems.

Develop equations of motion for this pendulum that give predictions that agree with the simulated behavior. Is the tension on the string correct for a gravitational field of 9.8 m/s

^{2}?Work on solving problems 1 through 4 from SAC127. The solutions are available, but make a serious attempt to solve the problems before looking at the solutions.

### Unit 4 Assessment

Please take this assessment to check your understanding of the materials presented in this unit.

**Notes:****There is no minimum required score to pass this assessment, and your score on this assessment**__will not__factor into your overall course grade.**This assessment is designed to prepare you for the Final Exam that will determine your course grade. Upon submission of your assessment you will be provided with the correct answers and/or other feedback meant to help in your understanding of the topics being assessed.****You may attempt this assessment as many times as needed, whenever you would like.**