Smooth ice reduces the unbalanced forces that would slow the hockey puck.
Galileo saw a pendulum and wondered why it took the same amount of time moving back and froth. He noted the time the pendulum took it to hold it to his heart. He noted his heart beats as a reference of the small times the pendulum took to reach a particular distance.
Explanation:
Density is mass divided by volume:
D = M / V
Given V = 79000 cm³ and D = 13.6 g/cm³:
13.6 g/cm³ = M / (79000 cm³)
M = 1,074,400 g
M = 1,074 kg
Round as needed.