Question

The plank is 5.1 meters long and has a mass of 9.2 kg, ack has a mass of 93.6 kg, and Diane has a mass of 64.2 kg. Assuming Diane sits at one end of the plank, how far from his end of the plank should Jack sit for the two of them to be perfectly balanced?

Answer 1

Answer:

The answer is 0.8 m

Explanation:

According the attached diagram, if we take the momentum in the point 0:

$\frac{m_{D}*5.1 }{2} =m_{J} *X$

Where

mD = mass of Diane = 64.2 kg

mJ = mass of Jack = 93.6 kg

Replacing:

$X=\frac{\frac{64.2*5.1}{2} }{93.6} =1.75m$

$\frac{L}{2} -X=Y=\frac{5.1}{2} -1.75\\Y=0.8m$