Question

1 multiple choice 1 point
which of the following is the coefficient of static friction?
$f_n$
$f_{sf}$
$\mu_k$
$\mu_s$
$f_{kf}$
2 multiple answer 1 point
check all of the following true statements about coefficients of friction
coefficients of friction measure how \sticky\ something is
coefficients of friction are measured in newtons
coefficients of friction measure the acceleration of an object
coefficients of friction are unitless

Explanation:

• For question 1:
• \(F_N\) represents the normal force.
• \(F_{sf}\) represents the static - friction force.
• \(\mu_k\) is the coefficient of kinetic friction.
• \(\mu_s\) is the coefficient of static friction.
• \(F_{kf}\) represents the kinetic - friction force.
• For question 2:
• Coefficients of friction measure the "stickiness" (or resistance to relative motion) between two surfaces.
• Since \(\mu=\frac{F_f}{F_N}\) (where \(F_f\) is the friction force and \(F_N\) is the normal force), and both \(F_f\) and \(F_N\) have the unit of force (Newtons), the coefficient of friction \(\mu\) is unitless.
• Coefficients of friction do not measure acceleration (\(a = \frac{F}{m}\) is for acceleration, where \(F\) is the net force and \(m\) is the mass) and they are not measured in Newtons (as shown by the formula \(\mu=\frac{F_f}{F_N}\)).

Answer:

1. \(\mu_s\)
2. Coefficients of friction measure how "sticky" something is; Coefficients of friction are unitless