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**Determine mass of a glider on an air track [solved]**

## Homework Statement

A 20.0 g mass is stringed to a glider on an air track through a pulley (https://www.physicsforums.com/attachment.php?attachmentid=30478&stc=1&d=1291794499"). I'm supposed to find the mass of said glider, assuming that the air track and pulley are frictionless and the string is massless.

Data from a graph:

V

_{1}= 0.143 m/s

V

_{2}= 0.377 m/s

Δt = 0.24 s

## Homework Equations

a = (V2 – V1) / Δt

F

_{net}= ma

## The Attempt at a Solution

a = (V2 – V1) / Δt

= (0.377 – 0.143) / 0.24

= 0.975 m/s

^{2}

Mass 1 (https://www.physicsforums.com/attachment.php?attachmentid=30479&stc=1&d=1291794499"):

Fnet = ma

F

_{n1}+ Fg

_{1}+ T

_{1}= -m

_{1}a

-m

_{1}g + T

_{1}= -m

_{1}a

-9.8m

_{1}+ T

_{1}= -0.975m

_{1}

+T = 8.825m

_{1}

Mass 2 (https://www.physicsforums.com/attachment.php?attachmentid=30480&stc=1&d=1291794499"):

Fg

_{2}+ T

_{2}= m2a

+m

_{2}g – T

_{2}= +m2a

(20.0)(9.80) – T

_{2}= 20.0(0.975)

196 – T

_{2}= 19.5

-T

_{2}= -176.5

Final Calculations:

+ T = 8.825m

_{1}

(+) – T = -179.84

---------------------

0 = 8.825m

_{1}– 179.84

8.825m

_{1}= 179.84

m

_{1}= 179.84/8.825

= 20 g

When the glider was weighted on a scale, it was said to be 429 g. So I have no idea what I'm doing wrong--am I getting the mass of the "20.0 g mass" here, or is this number just coincidental and irrelevant? Are the equations used incorrect? Thanks for any help.

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