posted by Tom on .
A cat walks along a uniform plank that is 4 m long and has a mass of 7 kg. The plank is supported by two sawhorses, one 0.44 m from the left end of the board and the other 1.5 m from its right end. When the cat reaches the right end, the plank just begins to tip. What is the mass of the cat?
If we remove the left end sawhorse, what mass could be put instead to keep the system in equilibrium with the cat at the right end of the plank?
Since the plank is beginning to tip, there is no weight on the left sawhorse.
The torque about the right sawhorse is
M•g •0.5 – m•g•1.5 = 0
m = = 2.33 kg