Question

Two children push on opposite sides of a door during play. both push horizontally and perpendicular to the door. one child pushes with a force of 165 n at a distance of 0.400 m from the hinges, and the second pushes at a distance of 0.450 m. what force (in n) must the second exert to keep the door from moving

Answer 1

From the principle of conservation of linear momentum
Force x distance1 = opposite force x distance 2
165 x 0.4 = 0.45 x F2
F2= 165x0.4/0.45
F2= 147N
The second child must exert a force of 147N to keep the door from moving.