Question

A small ferryboat is 3.90 m wide and 6.30 m long. when a loaded truck pulls onto it, the boat sinks an additional 5.00 cm into the river. what is the weight of the truck?

Answer 1

When the truck's weight is added to the boat, the boat sinks 5 cm deeper,
and displaces additional water whose weight is equal to the weight of the
truck.

The volume of the additional displaced water is

             (3.9 m) x (6.3 m) x (5.0 cm)

         =  (3.9 m) x (6.3 m) x (0.05 m)  =   1.2285 m³ .

The weight of that much water is the weight of the truck.

          Mass of 1 liter of water  =  1 kilogram

          1.2285 m³  =  1,228.5 liters  =  1,228.5 kg of water.

          Weight = (mass) x (gravity)

                      = (1,228.5 kg) x (9.8 m/s²)  =  12,039 Newtons.

                                                                  (about 2,708 pounds)