Math in the Workplace - Algebra

BOISE POLICE DEPARTMENT Law Enforcement Police Officer	Job Description: Traffic investigation

Problem:

Background:

A car travels 1.467 feet per second for every 1 mph.

The formula for speed (in miles per hour) is S = 30fd.

Feet per second (fps) = miles per hour (mph) x 1.467

Total Stopping Distance = (reaction time) x (fps) + skid length

d=Distance traveled

Time =

d v

Questions:

1. Assuming a reaction time of .75 seconds, how fast was car A traveling at the beginning of its skid? The coefficient of friction (f) on the road is .80. The coefficient of friction is given for different circumstances, such as dry pavement, snow floor, or black ice.

2. What was the total stopping distance of car A?

3. How long did it take car B to turn if driver A reacted immediately when car B began its turn?

BOISE POLICE DEPARTMENT

Solution:

1.	S =	30 x f x d
	S =	30 x .80 x 50
	S =	1200
	S = 34.64

 Speed = 35 mph at the start of the skid

2.  

fps = 35 x 1.467 = 51.345

Total stopping distance = .75 x 51.345 ft + 50 foot skid

Total stopping distance = 88.5 ft

Car A was about 88–89 feet from point of impact when car B started the left turn.

3.	Time =	d v
	Time =	90 ft 51.345

Time = 1.75 seconds for car B to begin turning and get hit

Math in the Workplace: Overview