WOLFRAM|DEMONSTRATIONS PROJECT

Block on a Frictionless Inclined Plane

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slope θ
releaseblock
The block speeds up as it slides down. How does the speed at the bottom depend on the steepness of the slope? Following Galileo, who did this type of experiment before Newton was born, you can investigate this using the slider and "trigger".
The Demonstration is a model showing the forces as "arrows" or "vectors". There are only two forces acting on the block: (1) the blue "normal" force, exerted by the plane on the block in a direction perpendicular or "normal" to the surface of the plane, and (2) the red gravitational force (
F
grav
, exerted downward by the Earth). These two forces "add" together (as vectors) to yield
F
net
, which points down the plane.
Newton's second law states that the rate of change in the speed is directly proportional to
F
net
.
As you change the angle, you can see that
F
grav
remains constant, while the normal force and
F
net
change as required to keep
F
net
equal to the vector sum of
F
grav
and the normal force.