Description Shape Area Triangle Quarter Circle Semicircle 0 Sector of Circle 0 One Quarter the Circumference of a Circle in the 1st Quadrant Half the Circumference of a Cicle Above the x – axis 0 Cone 0 Hemisphere 0

## Centre of Gravity Tables

Description Shape Area Triangle Quarter Circle Semicircle 0 Sector of Circle 0 One Quarter the Circumference of a Circle in the 1st Quadrant Half the Circumference of a Cicle Above the x – axis 0 Cone 0 Hemisphere 0

## Ladders on Rough Ground or Leaning Against a Rough Wall

Problems involving ladders usually involve taking moments and resolving vertically and horizontally. There are several points to remember: 1. A reaction at a surface can always be resolved into two components. a) A Normal Reactionwhich always acts perpendicular to a surface. b) A Force of frictionwhich always acts parallel to a surface. The relationship between […]

## Force and Power

One of the basic equations of physics is orIf the work is done in a timethen we can divide both sides byto obtain orwhereand We can generalise this equation: If a body is travelling at a velocityagainst a forcethen the power needed to overcome the force isIt should be noted that at any instant the […]

## Work Done to Overcome Friction

Energy is often lost when things move as friction is usually present and energy must be used to over come it. This usually means that the speed of a body at the end of a period of motion is less than it would have been, or that energy has to be given to a body […]

## Centres of Gravity of Lamina

We can find the distance of the centre of gravity from a line of a point by taking moments about the point for each part of the lamina. We equate this to the moment of the lamina as a whole and solve the equation to find the distance of the centre of gravity from the […]

## Equations for Projectiles

A projectile is a body that falls freely under gravity ie the only force acting on it is gravity. In fact this is never strictly true, since there is always air resistance for example, but these other forces are small compared to gravity in most circumstances so we ignore them. We can resolve the initial […]