Anyone can check whether my answer is correct regarding friction?

[cracktheegg]

1. The ratio of limiting friction to the normal reaction is known as
Answer

a)angle of friction.

b)angle of repose.

c)coefficient of static friction.

d)coefficient of kinetic friction.


Question 2


When a block is at rest on an inclined plane,
Answer

a)the friction force is equal to the static friction.

b)the friction force is equal to the kinetic friction.

c)the friction force is zero.

d)the friction force is less than the static friction.


Question 3


The coefficient of static friction is ______ the coefficient of kinetic friction.
Answer

a) less than

b)equal to

c) more than

d)dependent on

Homework Equations

Fs=urn

The Attempt at a Solution

1)c
2)a
3)c

 

[berkeman]

1. The ratio of limiting friction to the normal reaction is known as
Answer

a)angle of friction.

b)angle of repose.

c)coefficient of static friction.

d)coefficient of kinetic friction.


Question 2


When a block is at rest on an inclined plane,
Answer

a)the friction force is equal to the static friction.

b)the friction force is equal to the kinetic friction.

c)the friction force is zero.

d)the friction force is less than the static friction.


Question 3


The coefficient of static friction is ______ the coefficient of kinetic friction.
Answer

a) less than

b)equal to

c) more than

d)dependent on

Homework Equations

Fs=urn

The Attempt at a Solution

1)c
2)a
3)c

Can you explain your answer to question #2?

 

[cracktheegg]

I thinking the block at rest mean the slope is not high enough to make it move. Therefore I can only conclude that the static friction is equivalent to friction force

 

[haruspex]

I don't like question 2 at all. "Static friction" is a concept; the quantifiable entity is the frictional force that results.
Allowing that here it is being used as shorthand for static friction force, I agree with the answer in the OP.
But I harbour suspicions that the problem setter intends "static friction" to mean the limiting static friction force.

 

[HalfLostAndSearching]

I would say that your answers for questions 1 and 2 are correct. The coefficient of static friction is indeed the ratio of limiting friction to the normal reaction, and when a block is at rest on an inclined plane, the friction force is equal to the static friction. However, for question 3, I would say that the coefficient of static friction can be either less than, equal to, or more than the coefficient of kinetic friction. It depends on the materials and surfaces involved in the friction. It is not necessarily always one of these options. Therefore, I would suggest further research and experimentation to determine the coefficient of static friction in a specific situation.