Question

Consider a block on an incline plane. The coefficients
of static and kinetic friction between
the block and the incline are µs = 0.353 and µk = 0.31.
Calculate the critical angle θc, where the block just begins to slide.
Answer in units of ◦.

The block weighs 1kg.

Please help. I don't know what to do.

Answer 1

all that matters is mu static

normal force = m g cos T
so Friction force = .353 m g cos T
force down slope = m g sin T

m g sin T = .353 m g cos T

tan T = .353

Answer 2

so if i do tan^1(.353) that should be my answer?

Answer 3

yes

Answer 4

my computer said it was wrong...
I have online hw and im stuck on this one. i tried that answer and it said it was incorrect

Answer 5

I get 19.4 degrees to three significant figures

Answer 6

that is right. thx so much bro

Answer 7

You are welcome.

Answer 8

If you can, ive got two other problems that i don't know how to do.

A block is at rest on the incline shown in
the figure. The coefficients of static and kinetic
friction are µs = 0.62 and µk = 0.53,
respectively.
The acceleration of gravity is 9.8 m/s
2
What is the largest angle which the incline
can have so that the mass does not slide down
the incline?
Answer in units of ◦
.

Answer 9

just realized why it was wrong the first time. I was doing tan^-1(3.53