Tension force and horizontal pulling forces. How Newton’s Laws of Motion can explain the force of tension; how tension remains constant when the forces pulling on a rope from opposite ends and in opposite directions become unbalanced; tension and vertical pulling forces ; explanation of tension in a cable which is attached a light to a ceiling; tension in the cable of an escalator; tension at the molecular level.
In this article we investigate the force of friction which opposes the forward motion of objects; we look at the force that needs to be applied to an object before friction can be overcome and forward motion can occur. We explain static and kinetic friction, how friction comes in pairs and represents the interaction between two different surfaces; what happens when a surface is frictionless, how friction can help or harm.
Early theories about the motion of falling objects; characteristics of objects in freefall; how the shape,cross sectional area and mass of different objects affect the speed of objects in freefall; the hammer and feather experiment as carried out on the Moon in 1971; two different types of freefall ; Felix Baumgartner’s incredible jump from the edge of space; reaching terminal velocity.
This article investigates the three main forces of drag- namely aerodynamic drag, hydrodynamic drag and frictional drag (or skin drag). We consider the following: reasons why objects in forward motion slow down; effects of aerodynamic drag on cyclists and formula 1 racing cars; evolution of underwater predators with streamlined shapes; how dolphins have evolved to reduce skin drag.