## A visitor to the observation deck of a skyscraper manages to drop a penny over the edge. As the penny falls faster, the force due to air resistance increases. How does this affect the acceleration of the penny? a. The acceleration decreases b. The acceleration remains constant and not zero (my answer) c. The acceleration remains zero d. The acceleration increases.

October 13, 2019// Blog//

**Weight calculation:**

The weight by definition, is given by:

W = m * g

Where,

m: mass of the book box

g: acceleration of gravity

Substituting values we have:

W = 12 * 9.8

** W = 117.6 N**

** Calculation of normal force:**

For normal force, we make a free-body diagram in vertical direction, therefore, we have to:

Fn – W = 0

Rewriting we have:

Fn = W

Substituting values:

** Fn = 117.6 N**

**Calculation of the friction force:**

For the force of friction, we make a diagram of free body in horizontal direction, therefore, we have to:

96 – Fs = 0

Note: we equate to zero because the speed is constant, therefore, the acceleration is equal to zero.

Clearing we have:

** Fs = 96**

** Calculation of the coefficient of friction:**

By definition, we have to:

Fs = μFn

Clearing the coefficient of friction we have:

μ = Fs / Fn

Substituting values:

μ = 96 / 117.6

** μ = 0.82**