Forces
Properties of Forces
Effects of unbalanced forces
- change speed (positive or negative acceleration)
- change direction
- change shape
Examples of forces
- Friction
- Air resistance (or drag)
- Water resistance (or viscous drag)
- Tension
- Normal Reaction Force
- Magnetic
- Electrostatic
- Gravity
Remember, the last three are non-contact forces, the others are all contact forces.
Balanced and Unbalanced
A resultant force will have three possible effects; it can change:
- the speed of an object
- the direction of an object
- the shape of an object
The first two changes can be combined into changing the velocity of an object.
These changes will only happen if the forces acting on something are unbalanced. If the forces are balanced, then they will cancel each other out so the object will not change its shape and will continue to move at a constant velocity.
Remember, this velocity may be zero.
Friction
If an object has no force to move it along, it will always slow down over time; this is because of friction. Friction is a force that always opposes motion.
As the speed of an object increases, then so does the force of friction.
Friction can occur in three main ways:
- Friction between solid surfaces which are not moving, (static friction)
- Friction between solid surfaces which are sliding past each other - this can be reduced by using a lubricant, like oil in a car engine.
- Resistance or drag from from fluids, (liquids or gases) - this can be reduced by streamlining an object.