Mechanics - Laws of Motion - SS2 Physics Past Questions and Answers - page 3

The coefficient of friction is a dimensionless quantity that represents the relationship between the frictional force and the normal force between two surfaces. It is denoted by the symbol μ. The coefficient of friction provides information about the interaction between the surfaces and helps determine the magnitude of the frictional force.

 

A higher coefficient of friction indicates a stronger interaction and a higher frictional force, while a lower coefficient of friction suggests a weaker interaction and a lower frictional force. It plays a crucial role in various applications, such as determining the maximum angle at which an object can rest on an incline without sliding, calculating the force needed to overcome static friction and set an object in motion, and understanding the behaviour of objects on different surfaces.

Static friction and kinetic friction are two types of friction that exist between surfaces. Static friction is the force that opposes the motion of an object at rest, while kinetic friction is the force that opposes the motion of an object already in motion. The main differences between them are as follows:

- Definition: Static friction prevents the initiation of motion, while kinetic friction acts on objects in motion to slow them down.

- Behaviour: Static friction adjusts its magnitude to match the applied force, allowing objects to remain at rest until a force exceeds the maximum static friction. Kinetic friction remains relatively constant once an object is in motion, with its magnitude depending on the coefficient of kinetic friction and the normal force.

- Factors Affecting: The factors affecting static friction include the coefficient of static friction, the normal force, and the roughness of the surfaces. Kinetic friction is influenced by the coefficient of kinetic friction and the normal force.

Rolling friction is a type of friction that occurs when an object rolls over a surface. Unlike sliding friction, which occurs between surfaces in relative motion, rolling friction involves deformation and recovery of the object and the surface it rolls on. The magnitude of rolling friction depends on several factors, including:

- Nature of the surfaces: Softer materials or materials with higher elasticity tend to exhibit higher rolling friction.

- Surface roughness: Rougher surfaces can increase rolling friction due to increased contact area and deformation.

- Load or weight of the object: Rolling friction is generally proportional to the weight or load on the object.

- Wheel or surface properties: The design and characteristics of the rolling object, such as the size, shape, and material of the wheels, can influence rolling friction.

- Lubrication: The presence of lubricants or oils can reduce rolling friction by minimising surface-to-surface contact and reducing frictional forces.

Tension in ropes is a force transmitted through a flexible medium, such as a rope or cable, that is used to transmit forces or support loads. In inclined plane problems, tension plays a crucial role in determining the motion of objects on the incline. The tension force in the rope is responsible for counteracting the weight of the object and providing the necessary force to move it up the incline or maintain its equilibrium.

 

The tension in the rope is affected by the angle of the incline and the weight of the object. As the angle of the incline increases, the component of the weight parallel to the incline also increases. This results in an increase in the tension in the rope since the tension force needs to overcome a greater component of the weight. Similarly, as the weight of the object increases, the tension in the rope also increases to counterbalance the increased weight.

Friction plays a significant role in inclined plane problems, especially when determining the tension in the rope. Friction acts parallel to the incline and opposes the motion of the object. The friction force can be classified into two types: static friction and kinetic friction.

 

When an object is at rest on an inclined plane, the static friction force opposes the tendency of the object to slide down the incline. The static friction force adjusts its magnitude to exactly balance the component of the weight parallel to the incline, thereby maintaining equilibrium. Consequently, the tension in the rope is equal to the component of the weight parallel to the incline plus the static friction force.

 

When the object is in motion on the incline, the kinetic friction force comes into play. It opposes the motion of the object and has a constant magnitude, given by the coefficient of kinetic friction multiplied by the normal force. In this scenario, the tension in the rope is equal to the component of the weight parallel to the incline plus the kinetic friction force.

 

The coefficient of friction affects the tension in different scenarios. A higher coefficient of friction results in a higher friction force, which in turn requires a higher tension in the rope to overcome the increased friction. Conversely, a lower coefficient of friction requires less tension in the rope to overcome the reduced friction force.