A person with compromised pinch strength in their fingers can
only exert a normal force of 6.0 N to either side of a pinch-held
object, such as the book shown in (Figure 1) .
What is the mass of the heaviest book this person can
hold onto vertically before it slips out of his or her fingers? The
coefficient of static friction of the surface between the fingers
and the book cover is 0.60.
Express your answer to two significant figures and
include the appropriate units.
Heaviest book has weight
= (6 6) * 0.6 N
= 7.2 N
If m = mass of the heaviest book in kg
= 0.733 kg.
You have two normal forces (N) of 6N thus F = 2�N = 2*.6*6N =
Therefore the book cannot weigh more than 7.2 N.
m=W/g = 7.2N/(9.8m/s^2) = .735kg