Chapter 4

Signs of acceleration: Magnitude of velocity changes, indicating a change in speed Direction of velocity changes, indicating a change in orientation

Why can we not use the term velocity to describe this particles motion?

Why can we not use the term velocity to describe this particles motion?

Acceleration vectors always point to the center of a circular path!!!

When a race car is traveling around a circular track, which of the following terms can you use to describe its motion? Explain. A. velocity B. Speed C. acceleration

Recall a concept just learned at the end of chapter 3: Velocity is the first derivative of position Acceleration is the first derivative of velocity and the second derivative of position

Example 1: A particle along the x-axis has its position described by the function x=(2t2 – t +1)m, where t is in seconds. At t=2, what is the particles position? Velocity? Acceleration?

You must memorize the generic position formula for straight line motion: s= si + vit + 1/2at2 And then remember the derivative relationship!!!!

Trajectory of a particle is the result of x vs Trajectory of a particle is the result of x vs. y components and speed at each point is the derivative of position plugged into pythagorean theorem.

Example 2: A particles motion is described by two equations: Example 2: A particles motion is described by two equations: x= 2t2 and y= (5t + 5) Draw a graph of the particles trajectory. Create a graph of the particle’s speed as a function of time. x= 2t2 and y= (5t + 5) V = √ (4t)2 + (5)2

Looking at example 4.3, why must we “break” motion into parts of trips instead of continuous trips?