Explanation:
avg spd = total distance/total time
=80/8=10m/s
From the information given above,
Mass [M] = 28 g
Change in temperature = 29 - 7 = 22
Specific heat of iron = 0.449 [This value is constant]
The formula for calculating heat absorbed, Q is
Q = Mass * Specific heat of Iron * change in temperature
Q = 28 * 0.449 * 22 = 276.58 J<span />
Using the equation for period length for a pendulum, you get 32.829 meters.
I would look this one up on Google
