We assume that the person is seated at a distance d from
the edge of the table. Now we can look at the table in the following way: The table top
is a line with a pivot at the point where the leg meets the table top. The weight of the
table is placed uniformly on the line and provides a torque about the pivot. The
counteracting torque is provided by the weight of the person. For the table to not tip
over, the torque due to the weight of the person should be equal to the torque due to
the weight of the table top.
As the person is at a distance
d from the edge, the torque exerted is equal to (0.5 - d)*65 + Int [ (20/2.3)x dx], x=0
to x=0.5.
We need to take the integral as the weight of the
table top is uniformly distributed and at each point a torque is provided by it. Also,
as g is present on both sides of the equation it gets canceled and is therefore
ignored.
This is equal to 0.5*65 - 65d + (20/2.3)(x^2/2),
x=0 to x= 0.5
=> 0.5*65 - 65d + (10/2.3)(.5^2 -
0).
On the other side of the pivot, the torque due to the
weight of the table top is Int [ (20/2.3)x dx],x = 0 to x =
1.8
=> (10/2.3)[1.8^2 -
0]
Equating the two, we
get
0.5*65 - 65d + (10/2.3)(.5^2 - 0) = (10/2.3)[1.8^2 -
0]
=> 0.5*65 - 65d + (10/2.3)(.25) =
(10/2.3)(3.24)
=> 65d = (10/2.3)(2.5)+ .5*65 -
(10/2.3)(3.24)
=> 65d =
29.28
=> d =
29.28/65
=> d = .45
m
So the closest distance from the edge that the person can
sit is 45 cm. If the person moves closer to the edge, the table will tip
over.
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