Distance = 400 m, Displacement = 400 m in the direction of the straight line.
<u>Answer</u>
Part 1) Increase
Part 2) expand
Part 3) rise
<u>Explanation</u>
When the air is heated the molecules gain kinetic energy and starts to collide with walls of the ballon making it to increase it size.
Thus the volume of the balloon expands. When this happens the balloon and its content becomes less dense and it rises.
The initial kinetic energy of the boat and its rider is

After Sam stops it, the final kinetic energy of the boat+rider is

because its final velocity is zero.
For the law of conservation of energy, the work done by Sam is the variation of kinetic energy of the system:

where the negative sign is due to the fact that the force Sam is applying goes against the direction of motion of the boat.
Answer: 0.790 g/cm3
Explanation:
The density of acetone is 790 Kg/m3.
To convert from Kg to g we multiply by 1000 (1 Kg = 1000 g)
To convert from m3 to cm3 we multiply by 10∧6
So, The density of acetone in (g/cm3) = (790 x 1000) / (10∧6) = 0.79 g/cm3