Understanding Force

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Calculating Force Based On Apparent Weight (2)


Force Lessons

Newton's First Law of Motion
Newton's Second Law of Motion
Newton's Third Law of Motion
Weight and Mass
Calculating Force




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


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.


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.