Background information
Explain that buoyancy force is the force a liquid exerts on materials
placed in it. This force opposes the weight of the object. An example of
this is a beach ball in a pool. It is difficult to push the ball under
the water due to the buoyancy force the water is exerting upward on the
ball. This force is much greater than the force the ball in exerting
downward on the water due to its mass. That is why the ball floats. When
the mass of the object on the water increases to where it is exerting a
force greater than the buoyancy force of the water, the object sinks.
F=m x g. You can also discuss Archimedes principle: The buoyancy force
exerted on a body placed in a fluid is equal to the weight of the fluid
the body displaces.
For the second part, we will prove objects move when unbalanced forces
act on them. Newton’s first law says objects remain at rest or remain
moving until an outside force acts upon them. The boats will remain
stationary until acted upon by an outside force. This principle will be
used to move the boats with a sail and fan, where the fan will be the
outside unbalanced force operating on the boat. We will measure how far
that force moves the boat and discuss the forces that moved and stopped
the motion of the boat.