Two children, with masses 35kg (on the left) and 45kg (on the right), sit at opp

Question

Two children, with masses 35kg (on the left) and 45kg (on the right), sit at opposite ends of a 3.1m long seesaw with mass 24kg , with the fulcrum at its midpoint. A)With the seesaw horizontal, find the net torque on the seesaw. Express your answer to two significant figures and include the appropriate units. Assume the counterclockwise rotation as positive. B)With the seesaw horizontal, find its angular acceleration. Express your answer to two significant figures and include the appropriate units. Assume the counterclockwise rotation as positive.

Explanation / Answer

F1=35*9.8=343N at left end r1=1.55m
F2=45*9.8=441 at right end r2=1.55m
F3=24*9.8=235.2N at mid point r3=0m
net torque =F1r1-F2r2=343*1.55-441*1.55=-151.9N-m i.e clockwise

b)I1=mr1^2=3581.55*1.55=84

I2=45*1.55*1.55=108

I3=ml^2/12=24*3.1*3.1/12=19

I=84+108+19=192

=/I=151/192=0.78rad/s^2

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