The weight of a solid object in air is measured as 40 N, and the weight of this same object in water at 20◦C is measured as 25 N. Estimate the specific weight and volume of the object. A hot air...

The weight of a solid object in air is measured as 40 N, and the weight of this same object in water at 20◦C is measured as 25 N. Estimate the specific weight and volume of the object.

A hot air balloon has a diameter of 15 m, and the weight of the balloon plus attached load is 2 kN. To what temperature must the air in the balloon be heated to achieve liftoff? Assume standard sea-level conditions in the surrounding air.