Topic 1
Motion, forces, and energy — from vectors and kinematics to momentum, energy, and pressure.
OBJECTIVES:
By the end of this section, you will be able to :
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A scalar quantity is a quantity that has magnitude (size) only. Examples of scalars: distance, speed, time, mass, energy and temperature
A vector quantity is a quantity has magnitude and direction. Examples of vectors: force, weight, velocity, acceleration, momentum, electric field strength and gravitational field strength
Speed is the distance travelled per unit time
Acceleration is the change in velocity per unit time
Velocity is the speed in a given direction
Average speed is defined as total distance / Total time
An object is in free-fall when it is moving only under the influence of the earth’s gravity.
It is a value of the acceleration of free fall (g). On Earth, this value of g for any object that is near the surface is approximately constant at 9.8m/s2. [ In IGCSE examinations, this value is taken to be 10m/s2]
Mass is a measure of the quantity of matter in an object at rest relative to the observer
Weight is defined as a gravitational force on an object that has mass
Gravitational field strength is the force per unit mass
Density is defined as the mass per unit volume
Spring constant is defined as the force per unit extension. Its formula is: k=F/x
It is a point beyond which the spring crosses its elastic limit and becomes permanently deformed.
It states that, for a body of constant mass "m" and net force "F", we can state that F = ma, where F ( net force) and a (acceleration)/ Both are vector quantities.
Circular motion is defined as the movement of an object along the circumference of a circle or the rotation of an object along a circular path.
Solid friction as the force between two surfaces that may impede motion and produce heating.
It is a force acting in a direction that is opposite to the relative motion of the object moving with respect to the surrounding fluid. Fluid refers to liquids and gases
It is a measure of the turning effect of a force. Formula is moment = force × perpendicular distance from the pivot. The SI unit of moment of a force is Nm
For an object in equilibrium, the sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments about the same point and the net force acting on it is zero.
It is a point at which the weight of a body or system is supposed to be concentrated. In uniform gravity it is the same as the centre of mass.
Momentum=mass × velocity; recall and use the equation p = mv. The SI unit of momentum is kgm/s
Impulse= force × change in time. [ it is the time for which force acts]. The Si unit of impulse is Newton-second (Ns)
When 2 or more bodies interact (collide) in an isolated system, the total momentum stays the same.
A resultant force is the change in momentum per unit time. The unit is Newtons (N)
The energy possessed by an object, by virtue of its motion is called as kinetic energy.
When objects are placed in a gravitational field, they possess certain energy relative to their position in this gravitational field. This energy is called as the gravitational potential energy. Formula for the gravitational potential energy= mgh; here m=mass of the object, g=gravitational field strength and h is the height to which the object is raised.
The energy stored in the bonds of chemical compounds is called as the chemical energy.
Strain energy is the energy stored in an object due to its deformation.
It refers to the potential energy of a system of separated electric charges
The energy of a thermodynamic system is its internal energy. It is the energy associated with the random, disordered motion of molecules
Principle of conservation of energy states that " Energy can never be created nor destroyed. It can only be converted from one form to another. The total amount of energy in a system stays the same.
Work is= Force x displacement. Here the displacement is in the direction of the force. Unit of work is Joule.
One Joule refers to the work done by a force of 1 Newton, when it displaces a body through 1m in the direction of the force applied.
This refers to cells that are capable of converting light energy to electrical energy through photovoltaic effect
It is a panel consisting of many solar cells, designed to absorb sun’s rays for generating electricity or for heating purposes.
The energy of the naturally flowing air that is used to generate electricity is called as wind energy.
This is the type of energy that comes from resources that are easily replenished. Example: Energy from the sun, wind, etc.
This is the type of energy that comes from resources that are easily not easily replenished. Example: Energy from fossil fuels
Percentage efficiency= {[ Useful energy output] /Total energy input]} x 100 or { [ Useful power output] /Total power input]} x 100
Power is defined as the work done per unit time of power is defined as the energy transferred per unit time.SI unit power is Watts (W)
Pressure is defined as the force per unit area.SI unit of pressure if Pascals (Pa). Formula for calculating pressure due to solids=Force/Area; While the formula to calculate the pressure exerted due to liquids is=hpg. Where h is the height of the liquid column, p is the density of the liquid and g is the gravitational field strength.
Motion, forces, and energy — from vectors and kinematics to momentum, energy, and pressure.
Thermal physics — particle model, temperature scales, specific heat capacity and heat transfer.
Waves — general properties, reflection/refraction, TIR, lenses and the EM spectrum.
Electricity and magnetism — charge, current, circuits, electrical power and safety.
Earth & Solar System, stars and the universe — redshift, CMBR, life cycle of stars and more.
Nuclear model, ionising radiation, decay equations and half-life.
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