Now that we’ve gotten through the definition of Force, we
can start applying the physics to basic mechanics.
The basic question is when the block will begin to slide
down the incline. The block will begin
to slide when gravity overcomes friction.
note: To simplify the
equations, we first define the x-axis and the y-axis in accordance with the
incline. (see diagram).
Next we look at the forces acting on the block:
Gravity: As
previously discussed (long ago), the force due to gravity is the weight of the
object; the force acting on the block due to gravity. This force acts directly downward.
Friction: Friction is the resistance to movement of a
surface. If you place your block on a
rough surface, it less likely to slide than on a smooth surface.
Normal Force: A normal force is the resistance to
gravity. If you place your block on a
table, it doesn’t fall into the table because the table applies a force to the
block that equals the force due to gravity.
How does the block slide?
The block will slide when gravity overcomes friction. In this case this means that the x-portion of
the force due to gravity becomes larger than the x-portion of the force due to
friction.
Notice that gravity acts on the block at an angle compared
to the x and y axis. This means that part of the force acts in the x-axis and
part in the y-axis. The x portion of
gravity balances the x portion of friction when the block doesn’t move.
The block’s potential to slide is base only in the x-axis so
the normal force has no influence on the block’s sliding and can be
ignored. Only the x portion of gravity (gravity(x) in the diagram) and friction
which acts only in the x-axis determine whether the block slides.
When the angle of the incline is sufficient to make
gravity(x) exceed friction then the block will slide.
Is this it?
We’re nearing the end of basic physics. Next we’ll apply the block on the incline
principles to rotational movement …. Let’s face it, gymnastics isn’t about
standing still, it’s about rotating.
