# PHYS 2211 Module 3.4

## Motion with Constant Acceleration

3.4 Motion with Constant Acceleration

### Learning Objectives

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

• Identify which equations of motion are to be used to solve for unknowns.
• Use appropriate equations of motion to solve a two-body pursuit problem.

### Kinematic Equations for Motion with Constant Acceleration

Practice!

Discuss!

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

A car is traveling with an initial velocity v0 = 65 mph.  At t = 0, the driver puts on the brakes, which slows the car at a rate of ab = 6.5 m/s2.  At what time tf does the car stop, and how much farther xf does it travel?

You are traveling along an interstate highway at 37.0 m/s (about 83 mph) when a truck stops suddenly in front of you. You immediately apply your brakes and cut your speed in half after 4.0 s.

(a) What was your acceleration, assuming it was constant?

(b) How long did it take you to stop from the time you started to apply the brakes?

(c) What was your stopping distance?

At the instant a traffic light turns green, a car that has been waiting at the intersection starts ahead with a constant acceleration of 2.8 m/s2. At the same instant a truck, traveling at a constant speed of 20.0 m/s, overtakes and passes the car.

(a) How far beyond its starting point does the car overtake and pass the truck?

(b) How fast is the car traveling when it overtakes the truck?