Can I please see an example of how this equation is used to find the coefficient of kinetic friction

The class I'm taking is physics for scientists and engineers! I am completely stuck. Need help. I have attached the problem. Please view both attachments before answering. If you can please explain your answer so I can fully understand. Thank you!

A student is trying to determine the critical angle (0) at which block will slide down an incline. She knows the coefficient of static friction between the incline and the block is 0.53 and the coefficient of kinetic friction is 0.44. Neglect drag. Hint: One way to solve the problem is to solve for all quantities in terms of m, e and g (but not u), then use f= uN and a trig identity to solve for 0. What is the critical angle? 13 Would the the block slide if the incline angle were 35°? cannot be det check answers I Rain to st

A 1,380-N crate is being pushed across a level floor at a constant speed by a force F of 320 N at an angle of 20.0° below the horizontal, as shown in the figure a below. a) What is the coefficient of kinetic friction between the crate and the floor? (Enter your answer to at least three decimal places.)(b) If the 320-N force is instead pulling the block at an angle of 20.0° above the horizontal, as shown in the figure b, what will be the acceleration of the crate? Assume that the coefficient of friction is the same as that found in part (a).m/s2

Determine the smallest magnitude of force P in pounds for which motion of block B impends. The coefficient of friction at all surfaces in contact is μs = 0.21. (Neglect the weight of the wedge A.) _____________ lb.

ents Once I went skiing. I was at the bottom of a snow ramp with a speed of 14.0 m/s. Assuming that the coefficient of friction between the snow and the skis was 0.2 determine my speed at the top of the ramp. The angle theta with the horizontal was 25°. The rise of the snow ramp was h=3.5 meters high. h Skier Met < Previous OL 1

Consider a pulley system of the type shown in the figure above. Suppose that the upper pulley has no mass and the lower two pulleys have a total mass of  9.1 kg; the block attached to the lower pulleys represents a car engine of mass 115kg . a) What is the tension T  in the rope? Assume that all sloped segments of the rope are vertical. b) What force does the ceiling exert on the upper pulley, assuming you pull straight up on the rope?