In: Physics
Show that the acceleration of any object down a frictionless incline that makes an angle theta with the horizontal is a= g sin theta (note that the acceleration is independent of mass.
This is a very general question and has no certain answer because
you don't tell us which direction the force is
directed.
I will solve one solution in which the force you mention is the
weight of the object
Let
F = the force
m = mass of object (unknown)
g = gravity
a = acceleration down slope
? = angle of slope from horizontal
Fn = normal force of slope on mass
Ff = friction force of slope on mass
Fg = Force of weight (gravity) acting parallel to the
slope
? = coefficient of kinetic friction
as stated, the force is the weight of the mass
F = mg
If we draw a free body diagram
The normal force of the slope on the mass is
Fn = Fcos?
Fn = mgcos?
and the weight force acting parallel to the slope
is
Fg = Fsin?
Fg = mgsin?
Then the friction force of the slope on the mass
is
Ff = ?Fn
Ff = ?mgcos?
So the net force accelerating the mass will be the gravity force
parallel to the slope minus the friction force
Fnet = Fg - Ff
Fnet = mgsin? - ?mgcos?
Fnet = mg(sin? - ?cos?)
If we then compare this equation to the basic
equation
F = ma
we can see that
a = g(sin? - ?cos?)
which is the acceleration of the mass down the slope with no other
external forces acting on it.
If friction is negligable, ? ? 0, and this reduces
to
a = gsin?