The key objectives that were to be achieved by this experiment included the following: To measure the force of static friction and find out its relationship with the weight of an object. A further objective is to determine both the coefficients of static friction and the coefficient of kinetic friction for a particular block and track then compare this kinetic friction coefficient with the one obtained from a motion detector. Then finally determine whether the coefficient of kinetic friction depends on weight.
Static friction is therefore the force that opposes the motion of two surfaces or bodies that are in physical contact when the surfaces/bodies are at rest. On the other hand, kinetic friction applies to the force that counters the movement of surfaces or bodies that are already in motion and are in physical contact. Static friction is modeled using the equation below:
Fstatic ≤μs FN,
Where: μs is the coefficient of static friction
FN is the normal force exerted by a surface on the object
F static is static friction.
The normal force is equal and opposite to the weight of the body for a level surface. Kinetic friction is modeled using the equation below:
Fk = μk FN
Where: μk is the coefficient of kinetic friction.
FN is the normal force exerted by a surface on the object.
Fk is kinetic friction.
The applied force is usually canceled by the force of static friction (Fstatic) up to a level when the static friction reached its maximum (Fsmax). The block will start to slip only when the applied forces are greater than the maximum force of static friction and at this point, the value for the friction becomes the kinetic friction (Fk). the box will start to accelerate because it’s under a net force.
When a block is pulled across a surface. In this case, the force of kinetic friction is a function of the normal force and the coefficient of kinetic energy. When some weight is added to the block then the normal force also increases with the same magnitude and the force of friction also increases with the same magnitude. The experiments found out that
the amount of friction on the block and amount of weight have a direct linear relationship; if the amount of weight is doubled then the amount of friction also doubles.
For two similar surfaces, the coefficient of static friction is always greater than the coefficient of kinetic friction. Higher values of the coefficient correspond to the greater the force of friction. Both the coefficient of static friction and coefficient of kinetic friction depends on the nature and type of material that make up the two surfaces/bodies.
The coefficient of kinetic friction and coefficient of static friction depends on the nature of the surfaces that are in contact. Rough surfaces for instance will have larger values of both static and kinetic coefficient of friction.