Calorimeter Homework: Clock Period & Temperature Change

[mimi83]

Homework Statement

A clock is designed with a simple pendulum, consisting of a mass at the end of an aluminum rod, whose period is supposed to be equal to one second. The clock is designed to keep accurate time at 20.0°C, but is operated at a constant temperature of −80.0°C. (a) Will the clock run fast or slow? Explain. (b) How many periods will the pendulum go through before the clock is off by 1.00 s? (The coefficient of linear expansion of aluminum is 2.31×10−5 1/C°.)

Homework Equations

Q = cmΔT
Qw + Qo = 0
ΔL = LiαΔT

The Attempt at a Solution

i tried several time using those equation above, but it didnot give the right answer, please help or give me hints.thank

 

[LowlyPion]

Aren't you wanting to know the length of the pendulum?
http://en.wikipedia.org/wiki/Pendulum_(mathematics)#Rule_of_thumb_for_pendulum_length