Question

When given a question such as…“During an experiment, an object is placed on a disk that rotates about an axle through its center, as shown in Figure 1. The disk is a distance R =0.10  m from the center and rotates with a constant tangential speed of 0.60 ms. A free body diagram of the forces exerted on the block is shown in Figure 2 with an unknown force of friction. What is the force of friction exerted on the object?“How do I know what formula to use to plug in my values to?

Answer 1

ANSWER:

0.72 N

STEP-BY-STEP EXPLANATION:

Due to the rotation, the centrifugal force is also worked in the outward direction.

Then the friction force is equal to:

$F_C=\frac{mv^2}{r}$

We calculate the mass, like this.

$\begin{gathered} F=m\cdot g \\ m=\frac{F}{g}=\frac{2}{9.81} \\ m=0.2\text{ kg} \end{gathered}$

Replacing:

$\begin{gathered} F_C=\frac{0.2\cdot0.6^2}{0.1} \\ F_C=0.72\text{ N} \end{gathered}$