A block of mass m is held in equilibrium against a vertical wall by a horizontal force. If the coefficient of friction between the wall and the block is µ, the minimum value of the horizontal force is

AllieMD

7 years ago

The answer is D. mg/u

The horizontal force (F) is equivalent to the normal reaction (R), ie *F=R* = mg..
but The frictional force (Fr) acting vertically upward = the limiting frictional force (u) × normal reaction (R)
ie Fr = u×R.
To balance the vertical upward force(Fr) and vertical downward for (Mg)
Fr=mg. but Fr=uR
uR = mg... recall R=F
uF=mg
F = mg/u
Option D....

Adem1234

2 years ago

the answer is c
horizontal force= frictional force+weight of object
mg+umg=mg(1+u)
B

djayenimoney

4 years ago

Am confused right now 😢

kaelindaureaus380

3 months ago

the question clearly stated at equilibrium
meaning frictional force=normal reaction
uf=mg
f=mg/u
option D is legit

FANCY1234

4 years ago

The answer is D
F1=uF
For Equilibrum F1=MG
I.E fu=mg
FU=mg/u

Cheeannie

4 years ago

Is the answer not D??

Ozkam

2 months ago

I'm correct naa in that mg/coefficient of friction like my answer .

okraDEN2023

2 years ago

The answer should be B.

The horizontal force, F, acting on the block must be equal to at least the weight ( mg ) of the Block to keep it in equilibrium. So F ≥ mg

μ = Fr/R
Frictional Force Fr = μR Fr = μmg

Since frictional force, Fr, is already doing part of the work of keeping the block at equilibrium ( acting in opposition, acting vertically upwards while the weight of the block acts vertically downwards, trying to keep the Block from falling down ) then the minimum Force required to keep the block steady in equilibrium is F = mg - Fr
F = mg - μmg

F = mg ( 1 - μ )

okraDEN2023

2 years ago

The answer should be B.

The horizontal force, F, acting on the block must be equal to at least the weight ( mg ) of the Block to keep it in equilibrium. So F ≥ mg

μ = Fr/R
Frictional Force Fr = μR. Fr = μmg

Since frictional force, Fr, is already doing part of the work of keeping the block at equilibrium ( acting in opposition, acting vertically upwards while the weight of the block acts vertically downwards, Frictional Force is trying to keep the Block from falling down ) then the minimum Force required to keep the block steady in equilibrium is F = mg - Fr
F = mg - μmg

F = mg ( 1 - μ )