Question

A ladder is positioned on icy (frictionless) ground and is leant against a rough wall. At the instant of release it begins to slide.
Which diagram correctly shows the directions of the force P,W and R acting on the ladder as it slides?
A)

B)

C)

D)

Answer 1

Hint: Friction is defined as the resistance to the movement of one moving object relative to another. It is not a basic force, like gravity or electromagnetism.

Complete step by step solution: It is known that the normal force is always perpendicular to the surface by the flat surface at the point of contact.
Because in options B, C, D the lines of force are not perpendicular to the surface. Therefore, this option is wrong.

Hence option A is correct.

Additional Information: Friction is a force between two surfaces that are sliding, or trying to slide, across each other. For example, when we try to push a book along the floor, friction makes this difficult. Friction always works in the opposite direction to the direction in which the object moves, or is trying to move. Friction slows the moving object continuously. The amount of friction depends on the materials the two surfaces are made of. The higher the surface, the greater the friction produced. Friction also produces heat. If you rub your hands quickly, they will feel warm. Laws of Friction: When an object is moving, the friction is proportional and perpendicular to the normal force (N) and the friction is independent of the contact area as long as there is a contact area. The coefficient of static friction is slightly higher than the coefficient of kinetic friction.

Note: At times friction needs to be reduced. For example, we use oil to reduce friction between moving parts in a car engine. The oil keeps the surfaces separate and can flow between them. Reduced friction means less wear on moving car parts and less heat produced.