Cie igcse 0625 physics revision 2017 and 2018

Effects of forces A force may produce a change in size and shape of a body bending, twisting, compression, extension are the main ways for a body to change size, shape and motion if two forces are acting on the same line they are either acting together or against each other. the resultant force of two forces acting together is the sum of the forces in the direction that they were pulling/pushing. if they are acting against each other the resultant force is the bigger force minus the smaller force in the direction of the bigger force. if the forces are the same size they cancel each other out. to calculate the force, mass or acceleration of an object you can rearrange the equation force = mass X acceleration (provided you have the other two variables). if you threw a tennis ball, how hard the throw was depends on it’s mass and how fast the throw was.

Moment

Equilibrium  Centre of mass Scalers and vectors A scalar is a quantity that only has a magnitude (so it can only be positive) for example speed. A vector quantity has a direction as well as a magnitude, for example velocity, which can be negative. • More ways to add vectors (Pythagoras’s theorem and the parallelogram rule) : 

momentum and impulse  A moving object has momentum. This is the tendency of the object to keep moving in the same direction. It is difficult to change the direction of movement of an object with a lot of momentum. You can calculate momentum using this equation: Momentum (kg m/s) = mass (kg) × velocity (m/s) Impulse  The units of impulse and momentum are equivalent [N s = kg m/s].  Ft = mv – mu                             Impulse Newton's second law (F net  = m • a) stated that the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the mass of the object. When combined with the definition of acceleration (a = change in velocity / time), the following equalities result. F = m • a or F = m • ∆v / t   If both sides of the above equation are multiplied by the quantity t, a new equation results. F ...

Energy transfer    Energy form Description Kinetic energy The energy in a moving object is defined as that object’s kinetic energy. Gravitational potential energy The energy of an object, raised up against the force of gravity is that object’s Gravitational potential energy. Chemical energy The energy stored in chemical substances and which can be released in a chemical reaction is defined as chemical energy. Electrical energy The energy transferred by an electric current is called as electrical energy. Nuclear energy The energy stored in the nucleus of an atom is defined as nuclear energy. Strain energy The energy produced in an object when it is stretched or compressed is called as strain energy. Internal energy The energy of an object; the total kinetic and potential energies of its particles is defined as internal energy. Thermal (heat) energy The energy being transferred from a hotter place to a cooler place, as a result of the temperature difference between ...

Energy resources Sun is the source of energy for all our energy resources except geothermal, nuclear and tidal 

Work • Work is done when ever a force makes something move. The unit for work is the Joule (J). 1 joule of work = force of 1 Newton moves an object by 1 metre (again, if you employ the formula its common sense)  W=Fxd Work done (J) = Force (N) x Distance (m)  Power

Pressure  The relationship between pressure, force and area: Learn above formula by heart, if definition of pressure is asked in exam just write above formula in words as Pressure = force / area Theoretical understanding of the formula: If we look at the formula, the force is in numerator and area is in denominator. If force is large and area is small then the pressure would be bigger and vice versa. As If Force = 5 N and area is 5 m 2 then pressure is P= 5/5 =1 N/m 2   or  pascal However, if force = 5 N and area is 0.5 m 2 then pressure would be P = 5 / 0.5 = 10 N/m 2 Conclusion That is why camel can walk on the desert but a beautiful lady with a high and sharp heel can not. Reason, camel’s feet are wide so area is large and camel’s weight is divided on four legs. However, the beautiful lady’s weight is divided only on two feet and whose contact area with the ground is very small due to sharp heels. Example#1:  An elephan...

States of matter Molecular model Interpret the temperature of a gas in terms of the motion of its  ​ molecules. The higher the temperature, the faster the speed of the molecules. Temperature is a measure of the average speed of the molecules. Temperature is how hot something is; heat is energy that flows from hot  ​ substances to cold substances. Describe qualitatively the pressure of a gas in terms of the motion  ​ of its   molecules. At  a constant temperature, gas molecules move at a constant average speed,  ​ so that the force of the collision is the same ( on average ). If the gas is compressed into a smaller volume, there are more frequent  ​ collisions on each unit of area, so that the total force per unit area  ​ increases and the pressure increases. If a gas expands to a greater volume at a constant temperature, the pressure  ​ decreases. If you look at smoke through a micros...