Question

With two fingers, you hold a cone motionless upside down, as shown in figure. The mass of the cone is $2kg$, and the coefficient of static friction between you fingers and the cone is $\mu =1$. Find the minimum normal force (in Newton) that must be applied with each finger in order to hold up the cone.

• A. 25 N
• B. 75 N
• C. 50 N
• D. 100 N

Answer 1

The correct option is A 25 N

Frictional force,

$f=\mu N=N$ [$\mu =1$]

Now,

$2f\cos \theta =mg$

$2N.\frac{4}{5}=mg$

$N=\frac{5}{8}mg$