- #1

Hamiltonian

- 296

- 190

- Homework Statement
- A block of mass 20kg is placed on another block of 10kg the coefficient of static friction between the two surfaces = 0.3

the surface of contact between the 10kg block and floor is smooth. A force of 30N acts on the 20kg block. comment on the motion of the system

- Relevant Equations
- F = ma

the maximum value of friction between the surfaces of the blocks is ##60N##

the friction should be self-adjusting until this maximum value. Hence the force of friction in the given scenario should be = 30N but this is physically impossible as if this is the case the top block will be at rest and the bottom block will move.

hence I made the equations $$30 - f = 20a $$ $$10a = f$$

from this I got ##f = 10N##

but I don't understand why we are supposed to form these two equations are we supposed to do this out of necessity as we cannot say friction will be self-adjusting in the given scenario as it will lead to a physically impossible situation?

I don't as such have an issue with the question rather I don't understand why the above equations yield a correct answer as here friction is not-self adjusting.

the friction should be self-adjusting until this maximum value. Hence the force of friction in the given scenario should be = 30N but this is physically impossible as if this is the case the top block will be at rest and the bottom block will move.

hence I made the equations $$30 - f = 20a $$ $$10a = f$$

from this I got ##f = 10N##

but I don't understand why we are supposed to form these two equations are we supposed to do this out of necessity as we cannot say friction will be self-adjusting in the given scenario as it will lead to a physically impossible situation?

I don't as such have an issue with the question rather I don't understand why the above equations yield a correct answer as here friction is not-self adjusting.