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-100

-50

0

50

100

2 4 6 8 10

ft

min

minutes

A honey bee makes several trips from the hive to a flowergarden. The velocity graph is shown below.

What is the total distance traveled by the bee?

200ft

200ft

200ft

100ft

200 200 200 100 700 700 feet

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-100

-50

0

50

100

2 4 6 8 10

ft

min

minutes

What is the displacementdisplacement of the bee?

200ft

-200ft

200ft

-100ft

200 200 200 100 100 100 feet towards the hive

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To find the displacementdisplacement (position shift) from the velocityfunction, we just integrate the function. The negative

areas below the x-axis are subtracted from the totaldisplacement.

Displacement

b

a

V t d t

Distance Traveledb

aV t dt

To find distance traveleddistance traveled we have to use absolute value.

Find the roots of the velocity equation and integrate in

pieces, just like when we found the area between a curveand the x-axis. (Take the absolute value of each integral.)

Or you can use your calculator to integrate the absolutevalue of the velocity function.

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-2

-1

0

1

2

1 2 3 4 5

velocity graph

-2

-1

0

1

2

1 2 3 4 5

position graph

1

2

1

2

1

2

Displacement:

1 11 2 1

2 2

Distance Traveled:

1 11 2 42 2

Many exams have at leastone problem requiringstudents to interpretvelocity and positiongraphs.

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In the linear motion equation:

dS

V tdt

V(t) is a function of time.

For a very small change in time, V(t) can beconsidered a constant.

dS V t dt

S V t t We add up all the small changes in Sto getthe total distance.

1 2 3S V t V t V t

1 2 3S V V V t

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S V t t We add up all the small changes in Sto getthe total distance.

1 2 3S V t V t V t

1 2 3S V V V t

1

k

nn

S V t

1

n

n

S V t

S V t dt

As the number of subintervals becomesinfinitely large (and the width becomesinfinitely small), we have integration.

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This same technique is used in many different real-life

problems.

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Example: National Potato Consumption

The rate of potato consumptionfor a particular country was:

2.2 1.1tC t

where tis the number of years

since 1970 and Cis in millionsof bushels per year.

For a small , the rate of consumption is constant.t

The amount consumed during that short time is . C t t

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Example 5: National Potato Consumption

2.2 1.1t

C t The amount consumed during that short time is . C t t

We add up all these smallamounts to get the totalconsumption:

total consumption C t dt

4

2 2.2 1.1

tdt

4

2

1

2.2 1.1ln1.1

t

t

From the beginning of 1972 tothe end of 1973:

7.066

million

bushels

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Work:

work force distance

Calculating the work is easywhen the force and distance are

constant.

When the amount of force

varies, we get to use calculus!

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Hookes law for springs: F kx

x = distance that

the spring isextended beyondits natural length

k= spring

constant

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Hookes law for springs: F kx

Example:

It takes 10 Newtons to stretch a

spring 2 meters beyond its naturallength.

F=10 N

x=2 M

10 2k

5 k 5F x

How much work is done stretchingthe spring to 4 meters beyond itsnatural length?

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F(x)

x=4 M

How much work is done stretchingthe spring to 4 meters beyond its

natural length?

For a very small change inx, the

force is constant.

dw F x dx

5dw x dx

5dw x dx

4

05W x dx

4

2

0

5

2W x

40W newton-meters

40W joules

5F x x