AMY SHANTA BABOOLAL PHYSICS PROJECT: MECHANICS

ARISTOTLE’S ARGUMENTS One of his well known arguments is: to understand change, a distinction must be made between the form and matter of a living thing. For example a sculpture has the form of a human but the matter of bronze. If the bronze is molded into a new form, then a change has just occurred. One of his well known arguments is: to understand change, a distinction must be made between the form and matter of a living thing. For example a sculpture has the form of a human but the matter of bronze. If the bronze is molded into a new form, then a change has just occurred. He also thought of movement as a type of change, by observing what occurs when something is created or destroyed. He also thought of movement as a type of change, by observing what occurs when something is created or destroyed.

NEWTON’S THREE LAWS OF MOTION FIRST LAW: States that an object at rest tends to stay at rest and an object in motion continues to move with the same velocity, unless the object is acted upon by an unbalanced force. Inertia is the property which causes this change in motion. FIRST LAW: States that an object at rest tends to stay at rest and an object in motion continues to move with the same velocity, unless the object is acted upon by an unbalanced force. Inertia is the property which causes this change in motion. SECOND LAW: When a force acts on a body the rate of change of momentum is proportional to the applied force and takes place in the direction which the force acts, giving the equation: F = ma SECOND LAW: When a force acts on a body the rate of change of momentum is proportional to the applied force and takes place in the direction which the force acts, giving the equation: F = ma THIRD LAW: The statement used to describe this law is: For every action there is an equal and opposite reaction. THIRD LAW: The statement used to describe this law is: For every action there is an equal and opposite reaction.

WHAT IS A FORCE?  A force can be simply described as a push or a pull that causes a change in the state of motion of and object. When a force is applied to an object it may cause the object to change in: shape, size or motion.  Forces are represented using arrows and can be either contact or non – contact.  The unit for force is Newton.

DYNAMICAL SYSTEMS  When a an object is at rest, it takes a force to get it moving. Likewise, when an object is moving it takes a force to stop.  To explain Newton's first law, we can use the example of the X and brakes in a car. For the car to move from rest, a force has to be applied to the X similarly, for the car to stop a force has to be applied to the brakes.  In Newton’s second law, we see that multiplying the acceleration and mass of an object, we can get the force needed to move the object. For example to move a roller coaster with mass 4500kg moving at an acceleration of 1000ms -1, the force needed is 4500kg*1000ms -1 = N  When we walk, we exert a force on the ground, and the ground exerts an equal but opposite force on our foot, causing it to come back up. This proves Newton’s third law; each action has an equal and opposite reaction.

WHAT IS LINEAR MOMENTUM? Momentum is the physical quantity that takes into account both the mass and velocity of an object. It can be associated with Newton’s first and second laws. The linear mass of an object can be described as the mass of the object multiplied by its velocity i.e. p=mv It is measured in kgms -1.

LINEAR MOMENTUM An example used to demonstrate linear momentum is: A ball A of mass 5kg is traveling north at 6ms -1. Another ball B of mass 3kg is traveling south at 4ms -1. To find the momentum of each, we multiply the mass by the velocity. The momentum of ball A was found to be 30kgms -1 and the momentum of ball B was found to be 12kgms -1.

THE LAW OF CONSERVATION OF LINEAR MOMENTUM.  The statement used to describe the law of conservation of linear momentum is: Provided that the vector sum of the external forces acting on a system is zero, the total linear momentum of that system remains constant during collisions.  Momentum can be conserved for all interactions in which the vector acting on the force is zero.  When we use collisions, we see that the momentum before and after a collision are equal. After collisions, one of the following may occur:  Both objects come to a complete stop  Both objects move together in the same direction.  Both move off in the opposite direction. EXAMPLE: Two trains are on the same track. Train B of 200kg is stationary and train A is moving at 80ms-1 with mass 150kg. If they collide train A pushes train be off to a spade 30ms -1. What is the speed of train A? M 1 U 1 + M 2 U 2 =M 1 V 1 + M 2 V 2 (150*80) + (200*0)=(150*V 1 ) + (200*30) = 150V = 150V /150 = V 1 V 1 = 40 MS -1

CIRCULAR MOTION AND FORCES A force is needed when an object is moving in circular motion. The force keeps the object in place. Without the force, the object may move out of orbit. The force provides attraction between the two objects present. If a force is not present there will not be an attraction between the objects.

CIRCULAR MOTION AND FORCES When an object moves in uniform circular motion, it means that the object moves in a circle with constant speed, but not constant velocity. The velocity is not constant because the direction is continuously changing. When an object moves in uniform circular motion, it means that the object moves in a circle with constant speed, but not constant velocity. The velocity is not constant because the direction is continuously changing. When an object, in circular motion is accelerated towards the centre of the circle a centripetal force causes the acceleration and changes the direction without changing the speed. When an object, in circular motion is accelerated towards the centre of the circle a centripetal force causes the acceleration and changes the direction without changing the speed. The formula for finding the centripetal force in a circle is: F c = mv 2 /r, where r is the radius of the circle. The formula for finding the centripetal force in a circle is: F c = mv 2 /r, where r is the radius of the circle. EXAMPLE 1:When the Earth orbits the Sun, an unbalanced force, gravity, is present. This gravitational force of attraction between the Earth and the Sun, provides the centripetal force needed for circular motion. EXAMPLE 1:When the Earth orbits the Sun, an unbalanced force, gravity, is present. This gravitational force of attraction between the Earth and the Sun, provides the centripetal force needed for circular motion. EXAMPLE 2: When a car is going around a bend, the frictional force acting on the tires of the car provides the centripetal force needed. EXAMPLE 2: When a car is going around a bend, the frictional force acting on the tires of the car provides the centripetal force needed.