# PHYS 2211 Module 3.2

## Instantaneous Velocity and Speed

3.2 Instantaneous Velocity and Speed

### Learning Objectives

By the end of this section, you will be able to:

• Explain the difference between average velocity and instantaneous velocity.
• Describe the difference between velocity and speed.
• Calculate the instantaneous velocity given the mathematical equation for the velocity.
• Calculate the speed given the instantaneous velocity.

### Quick Calculus Review

Practice!

Discuss!

Consider how you would answer this question. Then bring this to class for a group discussion.

Suppose a particle moves along the x-axis. Its x-coordinate varies with time according to the expression x(t) = 8 + 3.8t + 2.5t2, where x is in meters and t is in seconds.

(a) Determine the displacement Δx of the particle in the time interval t = 9 s to t = 20 s.

(b) Calculate the average velocity in the time interval t = 9 s to t = 20 s.

(c) Find the instantaneous velocity of the particle at t = 18.4 s.