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

the force required to move the cart is divided by three or 33.33 n.

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.