Question

It takes 275n to set a stationary 77.3 crate in motion. what is the coefficient of static friction?

Answer 1

Note: I'm assuming the data 77.3 is the mass of the crate.

Answer:

$\mu_s =0.36$

Explanation:

The coefficient of static friction, called \mu_s is the ratio between the force needed to start moving an object above a rough surface (Fr), and the normal force the surface exerts on the object (N).

$\displaystyle \mu_s =\frac{Fr}{N}$

The normal force is numerical equivalent to the weight of the body if no other external forces are acting.

$N=m\cdot g$

The mass of the crate is m=77.3 Kg, thus its weight and normal force is:

$N=77.3\ kg\cdot 9.8\ m/s^2$

$N= 757.54\ Nw$

Now we calculate the coefficient:

$\displaystyle \mu_s =\frac{275\cancel{N}}{757.54\cancel{N}}$

$\boxed{\mu_s =0.36}$