Question
1.
A body
weighing 80 N stands in an elevator that is about to move. The force exerted by
the floor on the body as the elevator moves upwards with an acceleration of 5 ms^{2}
is ? (g = 10 ms^{2})
Solution:
The net
force on the body is given as follows:
R  mg
= ma
Where R is
the reaction, or the vertical upward force exerted by the floor of the elevator
on the body; m is the mass of the body, a is acceleration with which the body
moves upwards, mg is the weight of the body.
Therefore,
Since weight
of the body mg = 80 N
m =
80/10 = 8
mass
of body = 8 kg
Substituting known values in
R  mg = ma,
we have
R
 80 = 8 x 5
R =
40 + 80
=
120 N
The
force exerted on the body by the floor is 120 Newtons.
