When you move a chair across the floor, the force you push with must be stronger than the force of static friction resisting the chair's motion. Static friction is the force that keeps the chair at rest and must be overcome to initiate movement. This force depends on the coefficient of static friction (μ_s) between the chair's legs and the floor and the normal force (N), which is usually the weight of the chair. The minimum force FFF required to start moving the chair can be calculated by:
F>μs×NF>\mu_s \times NF>μs×N
where NNN is the normal force (approximately equal to the chair's weight if the floor is horizontal), and μs\mu_s μs is the coefficient of static friction. Once the applied force exceeds this frictional force, the chair will begin to move. After motion starts, the friction opposing movement is kinetic friction, which is usually slightly less than static friction, so less force is needed to keep the chair moving than to start it moving
. In summary:
- Your push must be stronger than the static friction force resisting the chair's initial movement.
- This frictional force equals the coefficient of static friction multiplied by the normal force (weight of the chair).
- Once moving, the force needed to maintain motion is slightly less due to kinetic friction being lower than static friction
Therefore, to move a chair across the floor, your push must overcome the static friction force holding it in place.
