N2 Engineering Science

Engineering Science Downloaded from hlayiso.com N2

Chapter 1: Dynamics MASS AND WEIGHT Mass (measured in kilograms) is the amount of matter a body contains while weight (measured in newtons) is the gravitational force acting on a body. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 1: Dynamics (continued) DISTANCE AND DISPLACEMENT Distance is the distance covered, regardless of direction and displacement is the straight line distance that a body moves. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 1: Dynamics (continued) SPEED AND VELOCITY Speed is the rate of change of distance and velocity is speed in a given direction or the rate of change of displacement. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 1: Dynamics (continued) CONSTANT VELOCITY When a body moves at a constant velocity, it is often useful to represent the relationship between the displacement and time graphically. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 1: Dynamics (continued) ACCELERATION When the velocity of a body increases, it is said to be accelerating, thus acceleration is the rate of change of velocity. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 2: Statics REVISION OF FORCES AS VECTORS A force possesses both magnitude and direction and is therefore a vector quantity. In order to represent a force fully, its point of application must be included in the vector or its nature must be stated. Therefore, in order to represent a force fully, the following must be indicated: • Magnitude; • Direction; and • Point of application or nature. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 2: Statics (continued) PARALLELOGRAM OF FORCES If two similar forces acting on a point are represented as vectors by two adjacent sides of a parallelogram, their resultant will be represented in magnitude and direction by the diagonal of the parallelogram drawn from that point. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 2: Statics (continued) COMPONENTS OF A FORCES When two or more forces can replace a single force and still have the same effect as that single force, they are termed components of that force. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 2: Statics (continued) MOMENTS The moment of a force is the turning effect of a force about a point. A spanner tightening a nut is an example of this. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 2: Statics (continued) BEAMS When a horizontal beam, resting on supports, is in equilibrium when acted upon by vertical forces, then; • Sum of clockwise moments = sum of anticlockwise moments about the same point, and; • Sum of upward forces = sum of downward forces. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 2: Statics (continued) A COUPLE A couple is two equal parallel forces acting in opposite directions, but not opposite each other. Tightening a wingnut or closing a tap with two fingers is probably the most common examples of a couple. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 3: Energy and momentum ENERGY Energy is the capacity to do work. Energy is measured in joules. Energy occurs in many forms such as thermal (or heat), chemical, electrical, potential, kinetic, magnetic and atomic energy. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 3: Energy and momentum (continued) POTENTIAL ENERGY (PE) Potential energy is the energy a body possesses by virtue of its “position” or “state of strain”. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 3: Energy and momentum (continued) KINETIC ENERGY (KE) Kinetic energy is the energy that a body possesses by virtue of its motion. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 3: Energy and momentum (continued) CONSERVATION OF ENERGY The law of the conservation of energy states that energy cannot be created or destroyed, but it can be changed from one form to another. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 3: Energy and momentum (continued) MOMENTUM Momentum is the quantity that a body possesses as a result of its motion. 𝑃𝑃 = 𝑚𝑚𝑚𝑚 Type equation here. Where P = momentum of the body; m = mass of the body; and v = velocity of the body. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 3: Energy and momentum (continued) ANGULAR MOMENTUM Linear momentum is proportional to the mass and velocity (in a straight line) of the body. When considering a rotating disc, the momentum is also proportional to the mass and the angular velocity of the body. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 4: Work, power and efficiency WORK Work is the measure of change of energy state. It is measured in joules. Work is done regardless of whether the force moves in a straight line or rotates about a point. 𝑊𝑊 = 𝐹𝐹xs Where W = work, F = effective force, and s = distance. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 4: Work, power and efficiency (continued) POWER Power is the rate of doing work. 𝑊𝑊 𝑃𝑃 = 𝑡𝑡 Where P = power, W = work, and t = time. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 4: Work, power and efficiency (continued) FORCE/DISTANCE GRAPHS Work done may also be determined graphically by making use of a work diagram. The distance moved is plotted on the x-axis of a graph and the effective force on the y-axis. The enclosed area will represent the work done. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 4: Work, power and efficiency (continued) WORK DONE ON A HORIZONTAL SURFACE The force required to move a body across a horizontal surface at a constant velocity, is that force required to overcome friction and wind resistance. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 4: Work, power and efficiency (continued) EFFICIENCY Efficiency is a measure of how effectively energy is converted from one form to another. 𝑜𝑜𝑜𝑜 𝑜𝑜𝑜𝑜 𝜂𝜂 = × 100% 𝑜𝑜 𝑜𝑜 𝑖𝑖𝑖𝑖 𝑖𝑖𝑖𝑖𝑖𝑖 Where 𝜂𝜂= percentage efficiency, output = output work done, and input = corresponding input work done. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 4: Work, power and efficiency (continued) WORK DONE ON AN INCLINED PLANE When the body considered moves up an inclined plane, a third resistive component appears; the resistance due to gravity. In the diagram: w𝑜𝑜𝑜𝑜𝑜𝑜 𝑑𝑑 𝑑𝑑 𝑑𝑑𝑑𝑑 = 𝑊𝑊 sin 𝜃𝜃 × 𝑠𝑠 𝑗𝑗 𝑗𝑗𝑗𝑗 𝑗𝑗 𝑗𝑗𝑗𝑗 Downloaded from hlayiso.com www.futuremanagers.com

Chapter 4: Work, power and efficiency (continued) WORK DONE IN ROTATION All work done by rotating machines is done by a torque (or turning moment). 𝑊𝑊 = 2𝜋𝜋𝜋𝜋𝜋𝜋𝜋 Where W = work done in rotation, N = number of revolutions, and ° T = torque. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 5: Mechanical drives and lifting machines BELT DRIVES Belt drives are used to transmit rotary motion and power from one shaft to a other. They can also be used to alter the axis of rotation of shafts, to change the speed or direction of rotation of a shaft or to act as force amplifiers. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 5: Mechanical drives and lifting machines (continued) CHAIN DRIVES The most common example of a chain drive is the chain used on a bicycle. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 5: Mechanical drives and lifting machines (continued) GEAR DRIVES Gear wheels are used to transmit rotary motion and power from one shaft to a parallel shaft in close proximity. They can also act as force amplifiers. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 5: Mechanical drives and lifting machines (continued) LIFTING MACHINES Lifting machines are mechanical devices designed to make work easier. These machines make it possible for a load larger than the applied effort, to be raised. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 5: Mechanical drives and lifting machines (continued) WHEEL AND DIFFERENTIAL AXLE The differential wheel and axle and simple differential winch are similar in operation and the same equations may be used for both, provided the diameter of the circle through which the effort of the differential winch moves, is considered. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 5: Mechanical drives and lifting machines (continued) DIFFERENTIAL PULLEY BLOCK A pulley block, which has a pulley with two diameters and slots into which a chain fits, is coupled to the snatch-block, which also has a pulley with slots, by means of an endless chain. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 5: Mechanical drives and lifting machines (continued) HYRDRAULICS A quantity of gas adjusts its volume and its shape to a vessel. A quantity of liquid will adjust its shape to the lower portion of a vessel, but it does not change its volume. Pressure is the force exerted on a surface per unit area. According to Pascal’s law, a confined fluid transmits externally applied pressure uniformly in all directions. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 6: Friction FRICTION When two surfaces are in contact and movement takes place, or tends to take place, a force appears which resists motion. This force is known as the force of friction. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 6: Friction (continued) FRICTION ON AN INCLINED PLANE The angle of friction is the largest angle to the horizontal that one body will rest on another before it starts sliding. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 7: Heat HEAT AND TEMPERATURE Heat is a form of energy and temperature is an indication of the degree of hotness or coldness of a body. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 7: Heat (continued) SPECIFIC HEAT CAPACITY Specific heat capacity is the amount of heat energy required to raise the temperature of 1 kg of a substance 1 °C (or 1 K). Downloaded from hlayiso.com www.futuremanagers.com

Chapter 7: Heat (continued) CONSERVATION OF HEAT When a hot substance is mixed or brought into contact with a cooler one, heat is transferred from the hotter substance to the cooler one until their temperatures are equal. This is referred to as the Principle of Conservation of Heat. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 7: Heat (continued) THERMAL EXPANSION The volume of most substances increases when their temperature is increased. In engineering, the increase in volume of a liquid or gas is of most importance. In the case of solids, the increase in area and length is of most importance. When a substance is cooled, the reverse takes place. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 7: Heat (continued) HEAT VALUE The calorific value of fuel is the quantity of heat released per unit quantity of fuel (a substance which is burned in order to release heat energy) completely burned. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 7: Heat (continued) STEAM Steam has many advantages and outstanding qualities. It is produced from water, which is plentiful in most areas and relatively cheap to obtain. Both water and steam are clean to use. Steam has a very high heat content and can store large quantities of heat energy, which can, in turn, be converted into useful work. It can also be condensed and used over and over again. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 8: Particle structure of matter PARTICLE STRUCTURE Familiar examples of matter are water, air, copper, tin, smoke, iron and salt. All matter is made up of extremely small particles called molecules. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 8: Particle structure of matter (continued) ATOMS An atom is the smallest part of an element that has all the characteristics of that element. Atoms are made up of electrons, neutrons and protons. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 8: Particle structure of matter (continued) ELECTROLYTES An electrolyte is a solution able to conduct electric current. Electrolytes can be used: • In cells (batteries); and • In electroplating and electro-refining processes. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 9: Electricity GROUPING OF RESISTORS • Resistors in series: • Resistors in parallel: Downloaded from hlayiso.com www.futuremanagers.com

Chapter 9: Electricity (continued) FACTORS INFLUENCING THE RESISTANCE OF A CONDUCTOR The resistance of a conductor depends on four factors, namely: • The type of material from which the conductor is made. • The length of the conductor in metres (m). • The cross-sectional area of the conductor in 𝑚𝑚2 . • The temperature of the conductor. Downloaded from hlayiso.com www.futuremanagers.com

Chapter 9: Electricity (continued) ELECTROMAGNETIC INDUCTION • Dynamically-induced emf is the generation of an emf by the relative motion between a magnetic flux and an electric circuit. • Mutual induction is the generation of an emf in one circuit by varying the current in another circuit. • Self-induced emf is the generation of an emf in a circuit by varying the current in that same circuit. Downloaded from hlayiso.com www.futuremanagers.com