Physics Unit 3: Dynamics - Explaining Motion Notes

 Types of Forces:

1. Weight is the downward pull of Earth on an object.
2. Contact force is the pull of the object on the Earth.
3. Friction is the opposing force to the motion of an object.
4. Drag is similar to friction. When an object moves in any fluid, there is friction between the object and the fluid. This opposing force is called Drag.
5. Tension is the restoring force in a string that is stretched. Similarly, tension also acts in Springs that are stretched.
6. Upthrust: An object placed in a fluid experiences a difference of pressure at its bottom and top surfaces. Pressure in fluids increases with depth.

When an object is dropped in a fluid, initially, its weight increases its speed. As speed increases, the fluid resistance increases proportionally.

Terminal velocity is reached when the fluid resistance is equal to the weight of the object.

There is more pressure on the lower surface than on the upper surface; this difference in pressure tends to push the object upwards. If the upthrust is greater than the weight of the object, then the object floats on the surface.