All the weight of the wooden board is bear by the support located at the centre of the rod, and the other support which is located at the end, will have no reaction force, or 0 reaction force.
Therefore the reaction at the centre support is equal to the weight of the board, while the support at the end has 0 reaction force.
Coefficient of static friction = tan(a) = 0.4
r = 740 m
g = 9.8 m/s²

v = √(9.8 × 740 × 0.4) m/s
v ≈ 53.85908 m/s
The cars will have equal speeds and the 2 kg car will have greater kinetic energy.
Convection means that hotter and less dense fluids have a tendency to rise while colder and more dense fluids sink.
The answer would be (A)
Hot water is denser than cold water and so hot water will be above the cold water.
:D