Question

How far from the wall a ladder of length 5 m must be placed if the ladder is to touch a point 3m above.

Answer 1

Answer:

Correct option is

C

μ=

8

3

Vertical force on ladder are gravitational force, mg at center of ladder and Normal force from ground N

1

at point B. Balancing forces N

1

=mg

Horizontal forces are, frictional force f=μN

1

=μmg at B, and normal force from the wall N

2

at A.

Balancing forces N

2

=f=μmg.

To prevent slipping, the torque about point B must be zero.

Torque of gravitational force is mg×

2

3

.

Torque of Normal force from ground N

1

is mg×0=0.

Torque of Normal force from wall N

2

is μmg×4.

Torque of frictional force is μmg×0=0.

Balancing torques, μ=3/8