Two kids create a makeshift seesaw by setting a 4-m long uniform plank on a saw horse. the saw horse is 0.5 m to the left of the center of mass of the plank. the child of mass m1 = 48 kg sits at the left end of the plank. the child of mass m2 = 35 kg sits 1 m to the right of the center of mass of the plank. what is the mass of the plank?

39kg

Explanation:

As this system is balanced on the saw horse, the total net torque by the children and plank gravity must be 0

Since child 2 and the plank center of mass are both on the right of the saw horse, their torque is in opposite direction, so so are their signs:

where m1 = 48 kg is the mass of the first child on the left at L1 = 1.5 m

           mp is the mass of the plank on the right of the saw horse Lp = 0.5 m

           m2 = 35 kg is the mass of the 2nd child on the right at L2 = 1.5 m

Substitute all the parameters above and we get

less than one you can't create energy

do you have a formula possibly