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

you have to draw the persons position over there

in simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. this is also known as upthrust.