# Module 3 – Forces and motion

## CollisionsCollisions

The principle of conservation of momentum is that, for a system of interacting objects, the total momentum in a specified direction remains constant, as long as no external forces act on the system. So, when two objects collide, the total momentum before and after the...

## 1 Newton’s Laws of Motion1 Newton’s Laws of Motion

Newton developed three laws of motion: An object will remain at rest or continue to move at a constant velocity unless acted upon by a resultant force. The net (resultant) force acting on an object is directly proportional to the rate of change of its momentum, and is...

## Mechanical Properties of MatterMechanical Properties of Matter

The area under a force-extension (or compression) graph gives the work done. This is transferred to elastic potential energy within the material. Elastic potential energy is given by: Tensile stress is defined as the force applied per unit cross sectional area of the...

## SpringsSprings

A pair of equal and opposite forces is required to alter the shape of an object. Forces that produce an extension (tensile deformation) are called tensile forces and forces that shorten an object (compressive deformation) are called compressive forces.  Hooke’s Law...

## Kinetic and Potential EnergiesKinetic and Potential Energies

The kinetic energy of an object is given by: The gravitational potential energy of an object in a uniform gravitational field is given by: When an object falls through a gravitational field, GPE is converted to KE. When it reaches the ground, its GPE is 0 and its KE...

## Work and Conservation of EnergyWork and Conservation of Energy

Work done is equivalent to the product of the force and the direction moved in the direction of the force. W=Fx Work done has the unit Nm or joule. It is also equivalent to energy transferred (energy is the capacity to do work).  If the force is applied at an angle to...

## Density and PressureDensity and Pressure

The density of an object is defined as its mass per unit volume. Mass is measured directly using a digital balance. Volume is measured either using measurements taken with a ruler, digital calliper of micrometer (for regular solids), or by displacement (for irregular...

## Linear MotionLinear Motion

There are five SUVAT equations involving motion in a straight line at a constant acceleration. When an object is accelerating under gravity with no other force acting on it, it is said to be in free fall. The acceleration of free fall is denoted by g, whose value is...

## Projectile MotionProjectile Motion

The vertical and horizontal motions of a projectile are independent of one another.  The vertical velocity changes due to acceleration of free fall, whereas horizontal velocity remains constant. This means that a projectile has a constant velocity in one direction and...

## DynamicsDynamics

Net force is the product of mass and acceleration. The unit of force is newtons (N). f = m × a. The mass of an object is absolute – it is constant for a specific object or particle. However, the magnitude of weight is variable; it depends on gravitational field...

## Motion With Non-uniform AccelerationMotion With Non-uniform Acceleration

Drag is the frictional force experienced by an object travelling through a fluid. Its magnitude depends on several factors, including the speed of the object, the shape (cross-sectional area) of the object, the roughness or texture of the object, and the density of...

## EquilibriumEquilibrium

The moment of a force is the turning effect of a force about some axis or point. It is defined by: Moment = force x perpendicular distance from the line of action of force from the pivot Moment = Fx The SI unit for the moment of a force is Nm.  The principle of...

## KinematicsKinematics

Definitions: Displacement: a vector quantity that refers to how far an object is from its original position. Instantaneous speed: the speed of a car over a very short period of time, found by drawing the tangent to the distancetime graph and determining its gradient....

## Module 3.5 – Newton’s laws of motion and momentumModule 3.5 – Newton’s laws of motion and momentum

17. The introduction of mandatory safety features in cars is a consequence of the scientific community analysing the forces involved in collisions and investigating potential solutions to reduce the likelihood of personal injury. Crash tests has allowed car...