
- A
- B
- C
- D
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Correct answer: C
- Geometry of the ladder
The ladder has length and its foot is away from the wall.
So the height reached on the wall is
Thus, the ladder forms a -- triangle.
- Forces acting on the ladder
Since the wall is frictionless:
- At the wall, only a horizontal reaction acts: .
- At the floor, the reaction has two components:
- horizontal friction force ,
- vertical normal reaction .
The resultant reaction of the floor is
The weight of the ladder is acting at the midpoint of the ladder.
- Force balance
Horizontal equilibrium
The only horizontal forces are:
- wall reaction ,
- floor friction .
Hence,
Vertical equilibrium
The only vertical forces are:
- floor normal upward,
- weight downward.
Hence,
- Torque balance about the foot of the ladder
Take moments about the foot, so the floor reactions produce no torque.
-
The wall reaction acts horizontally at the top of the ladder, at height . So its moment is
-
The weight acts at the midpoint of the ladder. Since the foot is at and the top at , the midpoint is at horizontal distance from the foot. So the moment of weight is
For rotational equilibrium, So,
Thus,
- Resultant reaction at floor
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