Engineering Science Notes and Tutorials

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ENGINNERING SCIENCE TUTORIALS ANDNOTES (SEM 1)

CHAPTER 8 : Atomic Structure

Question #1: The first part of an atom to be discovered was the(A). proton.(B). neutron.(C). electron.

(D). nucleus.

Question #2: Most of the volume of an atom is occupied by(A). electrons.(B). protons.(C). neutrons.(D). empty space

Question #3: The atomic number of an atom identifies thenumber of(A). protons.(B). neutrons.(C). quantum orbits.(D). excited states.

ANSWER : C,D,A

Question #4: The simplest model of the a tom is shown in the diagrambelow. Please label them :



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Atomic Structure (Fill in the blanks) Atom is the smallest particle of matter. It consist of three particles,called proton, electron and neutron. Protons and neutrons are placed atthe center of the atom and electrons are placed around the center.Picture given below shows, structure of atom and locations of protonneutron and electron in atom.



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Center of the atom, including protons and neutrons, is called alsonucleus and circles around nucleus are called orbits.

Protons: Protons are positively charged particles of atoms. They arelocated in nucleus, and have mass. We show protons with letter "p".

Electrons: Electrons are negatively charged moving particles of atoms.They are located around the nucleus on orbits, and have no mass (verysmall). We show electrons with letter "e".

Neutrons: Neutrons are charge-less particles of atoms. They arelocated in nucleus, and have mass. We show neutrons with letter "n".

Fill in the blanks

Atomic

Symbol

AtomicNumber

Protons Neutrons Electron AtomicMass

B 5 5 6 5 11

Na 11 11 13 11 24

Mo 42 42 53 42 95

Ti 81 81 125 81 206

Yb 70 70 101 70 172

Sg 106 106 159 106 265



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CHAPTER 7 : HEAT vs TEMPERATURE

Heat and temperature are related and often confused. More heatusually means a higher temperature.

Heat (symbol: Q ) is energy. It is the total amount of energy (both kineticand potential) possessed by the molecules in a piece of matter. Heat ismeasured in Joules.

Temperature (symbol: T ) is not energy. It relates to the average(kinetic) energy of microscopic motions of a single particle in thesystem per degree of freedom. It is measured in Kelvin (K), Celsius (C)or Fahrenheit (F).

Exercise1. How much heat energy is needed to raise the temperature of 3kg of copper by 6 K?(Specific heat capacity of copper = 385 J/(kg K)

Heat energy = mass x specific heat capacity x temperature change= 3 x 385x 6 = 6930J

2. What is the rise in temperature of 5 kg of water if it is given 84

000 J of heat energy?Specific heat capacity of water = 4200 J/(kg K).

Heat energy input = 84000 = 5x4200x temperature riseTemperature rise = 84000/[5x4200] = 4 K

3. How much heat is lost by 3 kg of lead when it cools from 1000 oCto 200 oC?Specifc heat capacity of lead = 126 J/(kg K)

Heat energy given out = 3x126x80 = 30240J

Sensible heat

When an object is heated, its temperature rises as heat is added. Theincrease in heat is called sensible heat. Similarly, when heat is removed froman object and its temperature falls, the heat removed is also called sensibleheat. Heat that causes a change in temperature in an object is calledsensible heat.

Latent heat

All pure substances in nature are able to change their state. Solids can



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become liquids (ice to water) and liquids can become gases (water to vapor)but changes such as these require the addition or removal of heat. The heatthat causes these changes is called latent heat.

Specific latent heat of vaporisation is defined as the amount ofheat energy needed to change unit mass of a substance fromliquid phase to gaseous phase without a change of temperature.

Specific latent heat of fusion is defined as the amount of heatenergy needed to change unit mass of a substance from solidphase to liquid phase without a change of temperature

Exercise1. Frost is form due to change of state from vapor to solid.

a. True

b. False

2. An increase in pressure result in an increase in the freezingpoint of a substance.

a. True

b. False

3. The process by which a _________ change into a gaseousstate at a certain fixed temperature by the absorption of heat iscalled vaporization.

a. Liquid

b. Solid

Answer : a,b,a



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Find the values of 40 ºC in Fahrenheit and Kelvin thermometers.



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Differences between Heat and Temperature

• Heat is a type of energy, but temperature is not energy.• Heat depends on mass of the substance, however; temperature does

not depend on the quantity of matter. For example, temperatureof one glass of boiling water and one teapot of boiling water areequal to each other; on the contrary they have different heat sincethey have different masses.

• You can measure temperature directly with a device calledthermometer but heat cannot be measured with a device directly.You should know the mass, temperature and specific heatcapacity of that matter.

• If you give heat to a matter, you increase its temperature or change itsphase.

CHAPTER 6 : WORK, POWER AND ENERGY

The definition1)Work done = Work done in moving a body is equal to theproduct of force exterted on the body & the displacement of the

body in the direction of the force.

Unit = Nm = J(Joule)

2) Energy = The ability to do work.The amount of energypossessed by a body is equal to the amount of work it can dowhen its energy is released.

Unit = J(Joule)

3) Kinetic Energy = The energy of a body due to its motion

Unit = 1/2 mv^2

4)Potential Energy = The energy of a body due to its position or

change in shape.



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Unit = mgh

5)Power = In terms of work done : It is defined as the rate of doing

work.In terms of energy : It is defined as the rate at which energy isconsumed.

Unit = W(Watt)

6)Law of conservation of energy = According to it energy canneither be created nor be destroyed but can change from oneform to another. During a change of energy the total energyremains the same

Formula of work 1 - When the displacement is in the directionof force

Work done,

W = F!

s

Example 2

Diagram above shows a 10N force is pulling a metal. The friction between the block and the floor is 5N. If the distance travelled bythe metal block is 2m, find

• the work done by the pulling force• the work done by the frictional force

Asnwer:



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(a) The force is in the same direction of the motion. Work done bythe pulling force,

W = F ! s = (10)(2) = 20J

(b) The force is not in the same direction of motion, work done bythe frictional force

W = F ! s ! cos180 o= (5)(2)(-1) = -10J

Formula of Work 2

Example 1

A force of 50 N acts on the block at the angle shown in the

diagram. The block moves a horizontal distance of 3.0 m. Calculatethe work being done by the force.



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Answer:

Work done, W = F ! s ! cos ! W = 50 ! 3.0 ! cos30 o = 129.9J

Formula of Work 3Work Done to Move Object UpwardWork Done Against the Force of Gravity

Example 3Ranjit runs up a staircase of 35 steps. Each steps is 15cm in height.Given that Ranjit's mass is 45kg, find the work done by Ranjit toreach the top of the staircase.

Answer :

In this case, Ranjit does work to overcome the gravity. Ranjit'smass = 45kg Vertical height of the motion, h = 35 ! 0.15 Gravitational field strength, g = 10 ms -2 Work done, W = ?

W = mgh = (45)(10)(35 ! 0.15) = 2362.5J

Finding Work Done from a Force - Displacement Graph

Force - Displacement Graph



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Example 4

The graph above shows the force acting on a trolley of 5 kg massover a distance of 10 m. Find the work done by the force to movethe trolley.

Answer :

In a Force-Displacement graph, work done is equal to the area below the graph. Therefore, work done

W = ! x 8 x 10 = 40J

Card 6: What is Energy

EnergyEnergy is defined as the capacity to do work .

Work is done when energy is converted from one form toanother.

Unit: Nm or Joule(J)



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Card 7: Kinetic Energy

Kinetic EnergyKinetic energy is the energy of motion.

The Law of Conservation of Energy

Energy in a system may take on various forms (e.g. kinetic,

potential, heat, light).

The law of conservation of energy states that energy mayneither be created nor destroyed. Therefore the sum of allthe energies in the system is a constant.

The most commonly used example is the pendulum:



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The formula to calculate the potential energy is:

PE = mgh

The mass of the ball = 10kg The height , h = 0.2m Theacceleration due to gravity , g = 9.8 m/s^2 Substitute the valuesinto the formula and you get:

PE = 19.6J (J = Joules, unit of energy)

The position of the blue ball is where the Potential Energy(PE) = 19.6J while the Kinetic Energy (KE) = 0.

As the blue ball is approching the purple ball position the PE isdecreasing while the KE is increasing. At exactly halfwaybetween the blue and purple ball position the PE = KE.



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The position of the purple ball is where the Kinetic Energy isat its maximum while the Potential Energy (PE) = 0.At this point, theoretically, all the PE has transformed into KE.

Therefore now the KE = 19.6J while the PE = 0.

The position of the pink ball is where the Potential Energy(PE) is once again at its maximum and the Kinetic Energy (KE)= 0.We can now say and understand that:

PE + KE = 0

PE = -KE

The sum of PE and KE is the total mechanical energy:

Total Mechanical Energy = PE + KENOTE: This is with the abscence of outside forces such as

friction Using our common sense we know that it's impossible for thependulum to swing higher than the height h without giving it apush yourself. If there was no friction , the pendulum wouldswing back and forth forever because of the law of conservationof energy.



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Multiple Choice Questions

1. An example of Kinetic Energy would be:

a) a moving car

b) a stretched rubber band that was just released

c) a charge particle in an electric field

d) all of the above

2. An example of Potential Energy would be:

a) a moving carb) a battery

c) a book resting on a table

d) both b and c

3. Which is not an example of Solar Radiation

a) microwaves

b) magnetism

c) gamma rays

d) visible light

4. An example of a system having both kinetic and potential energywould be:

a) a book resting on a table

b) a piece of sugar

c) an object in free fall

d) a stretched rubber band



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5. Which of the following statements is not correct

a) energy is the capacity to do work

b) Work can be express as Force x Distance

c) power is the amount of work done in a unit of time

d) the unit of power is the joule

Answer : d,d,b,c,d

CHAPTER 5 : NEWTONS LAW OF MOTION



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xerc i se

1. Who was the scientist who gave us the Laws ofMotion?

Answer: Sir Isaac Newton

2. How many Laws of Motion are there?

Answer: three

3. What is another name for the first law of motion?

Answer: Law of Inertia

4. Which law explains why we need to wear seatbelts?

Answer: First Law of Motion

5. Which law says that force is equal to mass timesacceleration (F=MA)?

Answer: Second Law of Motion

6. Which law says that heavier objects require moreforce than lighter objects to move or accelerate them?

Answer: Second Law of Motion

7. Which law explains how rockets are launched into

space?



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Answer: Third Law of Motion

8. Which law says that for every action there is an

equal and opposite reaction?

Answer: Third Law of Motion



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• Exercise •• 1. Which of Newton's Laws of Motion is called the Law of Inertia?

A) 1stB) 3rdC) 2 nd

2. Which of Newton's Laws of Motion states that objects at rest tend to stay atrest and objects in motion tend to stay in motion unless acted upon by anunbalanced force?

A) 2ndB) 1stC) 3rd

3. The tendency of a moving object to continue in a straight line or astationary object to remain in place is called -

A) inertiaB) forceC) actionD) reaction

4. Which of Newton's Laws of Motion states that force equals mass timesacceleration?

A) 3rdB) 2ndC) 1 st

5. According to Newton's 2nd Law of Motion, force equals - A) mass divided by accelerationB) mass times accelerationC) mass subtract accelerationD) mass plus acceleration

6. Which of Newton's Laws of Motion states that for every action, there is an

equal and opposite reaction? A) 2ndB) 3rdC) 1 st

7. Which of the following is defined as a push or a pull? A) forceB) accelerationC) decelerationD) mass



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8. When a teacher stands at the front of the class, the force of gravity pullsher toward the ground. The ground pushes back with an equal and oppositeforce. This is an example of which of Newton's Laws of Motion?

A) 1stB) 2ndC) 3 rd

9. An object's inertia depends on its mass. A) TrueB) False

10. How much force is needed to accelerate a 90 kg skier 2 m/s 2? A) 180 kg/ms 2 B) 180 NC) 92 ND) 45 kg/ms 2

Answer : a,b,a,b,b,b,a,c,a,b

CHAPTER 4 : VELOCITY AND ACCELERATION

Assignment HelpMotion in One Dimension - Displacement, Velocity and AccelerationGraphs, Physics(i) Variation of acceleration (a), velocity (v) and displacement (x)with respect to time for different types of motion.



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Exercise

1. The units for acceleration are: a) m/secb) m/sec " c) secd) (m/sec) "

2. Which of the following are true about acceleration?

a) Acceleration is a change in velocity

b) An applied force is required for acceleration to occur

c) Acceleration can be either + or - in value.

d) All of the above



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3. In the graph shown above for an accelerating object, the accelerationis closest to?

a) 1 meters/second "

b) 2 meters/second "

c) 3 meters/second "

d) 4 meters/second "

4. The units for velocity are:

a) m/sec "

b) sec.

c) miles

d) m/sec

5. The slope of the graph of velocity vs. time (x-axis, velocity; y-axis,time) is:

a) distance

b) acceleration

c) speed

Answer : b,d,b,d,b



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CHAPTER 3 : MOMENT OF FORCE

Multiple Choice Questions

1. Which of the following are contact forces?

a) magnetic forces

b) gravity

c) air resistance

d) electrostatic forces

2. Which of the following are action at a distance forces?

a) air resistance

b) normal forces

c) magnetic forces

d) frictional forces

3. What is the force that opposes the relative motion or tendency tosuch motion of two bodies in contact

a) magnetism

b) the normal force

c) gravity

d) friction

4. 1 kg-m/sec/sec is equal to--

a) 1 Newton

b) 1 pound

c) 1000 newtons

d) none of the above



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5. Which of the following statements is not correct a) air resistance is a forceb) mass is the result of the force of gravityc) to accelerate an object requires a forced) weight is the force of gravity

Answer : c,c,d,a,b

CHAPTER 1 : PHYSICAL QUANTITIES ANDUNITS

Displacement, Velocity and Acceleration



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There are three categories of conversion of units are as the examplebelow:

Example:

Category 1

a. Convert 1 kg to unit gram 1 kilogram = 1000 grams

b. Convert 1 milligram to unit gram

1 milligram = 0.001 gramsc. Convert 30 ms to unit second 30 ms = 30 x 10 -3 s

= 3.0 x 10 -2 s

d. Convert 84 km to unit metre 84 km = 84 x 10 3 m

= 8.4 x 10 4 m

Category 2

a. Convert 5 cm 2 to unit m 2

5 cm 2 = 5 cm x 1 cm= (5 x 10 -2) m x (1 x 10 -2)m= 5 x 10 -4 m 2

b. Convert 100 mm 3 to unit m 3 100 mm 3 = 100 mm x 1 mm x 1mm

= (100 x 10-3

) m x (1 x 10-3

) m x (1 x 10-3

) m= 1.0 x 10 -7 m 3

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