A rectangular boat is 7 m wide and 7 m long. After a truck pulls onto the ferry, the boat ends up with a depth of 1 cm submerged under the water.

Question

What is the combined weight of the truck and the ferry? (Assume the density of water is 1000 kg/m3.) 

Answer 1

Find the volume of water displaced by the boat, when truck is the boat , say V

Weight of water displaced = V x(density of water)xg

By Archimedes Principle this equals the combined weight of truck and the boat.

W= 7m x 7m x 1cm x (1m/100cm) x1000kg/m³x10m/s² = 4900N