# Pulley question involving moment of inertia, and equilibrium between water and ice

1. Jan 20, 2013

### anuragpapineni

Two masses, 300 g and 400 g, are connected by a cord that passes over a pulley with a radius of 6.64 cm (an Atwood's machine). When released from rest, the 400-g mass falls 60 cm and the 300-g mass rises 60 cm in 4.00 seconds. Find the rotational inertia of the pulley.

Four 100-g ice cubes at a temperature of -20° C are dropped into an insulated cup containing 800 g of water at a temperature of 44° C. Find the equilibrium temperature of the mixture.

These two questions were on a recent competition I was at. The first one had an answer of 0.0546 but I'm not sure how I got there. For the second I kept getting 0 degrees Celsius which was wrong. The other answer choices were
B. 1.41° C
C. 2.82° C
D. 5.64° C
E. 11.3° C

help solving either is appreciated

2. Jan 20, 2013

### haruspex

Re: Pulley question involving moment of inertia, and equilibrium between water and ic