# Frictional Force

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## Frictional Force

Friction slows things down. If an object has no force, it will always slow doen and stop due to friction.

Friction acts in the opposite direction to movement. When 2 surfaces are in contact with each other or when an object passes through a fluid, is friction.

To travel at a steady speed, the driving force needs to balance the frictional force.

Resistance / Drah from fluids: most resistive forces are caused by air resistance or drag. To reduce the amount of air resistance or drag there is on an object, the shape of the object needs to be streamlined.

Drag increases as the speed increases: frictional forces from fluids increases with speed. A car has more friction to work against when travelling at a faster speed, this causes it to be harder to maintain a steady speed.

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## Terminal Velocity

Objects falling through fluids reach a terminal velocity.

When falling objects just start to fall, the force of gravity is more than the frictional force slowing them down, they start to accelerate...As they speed up, the friction builds up. -This reduces the acceleration until the friction force is equal to the accelerating force . It has then reached its TERMINAL VELOCITY and will then fall at a steady speed.

The terminal velocity of falling objects depends on their shape and area.

The accelerating force on all falling objects is gravity. Air resistance causes things to fall at different speeds. The terminal velocity of any object is determined by its drag compared to weight. The frictional force depends on shape and area.

R = W

resistance = weight

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