Chapter 1 Form 4 - Tutorial 1 (Physics)

Based Quantity and Derived Quantity
1.       A physical quantity is a quantity that can be measured
2.       A base quantity is a physical quantity that cannot be defined in terms of other physical quantities.
Base Quantity
SI Unit
Symbol
Mass, m
Kilogram
kg
Length, l
Meter
m
Time, t
Second
s
Temperature, T
Kelvin
K
Current, I
Ampere
A
Table 1.1
3.       Table 1.1 shows the five base quantity with their respective SI units.  (MLTTC)
4.       A derived quantity is a combination of various basic quantities. Units for derived quantities are known as derived units.
Derived Quantity
Relationship with the base quantity
Derived Unit
Volume
Length(m) x Breadth(m) x Height(m)
m3
Density
(Mass(kg))/(Volume(m^3))
kg m-3
Acceleration
(Change in Velocity(〖m s〗^(-1)))/(Time Taken(s))
m s-2
Velocity
(Displacement(m))/(Time(s))
m s-1
Momentum
Mass(kg) x Velocity(m s-1)
kg m s-1
Force
Mass(kg) x Acceleration(m s-2)
kg m s-2 (N)
Impulse
Change of Momentum
(kg m s-1)
[ Ft=m(v-u) ]
kg m s-1 (N s)
Energy
Force(kg m s-2) x Displacement(m)
kg m2 s-2 (J)
Power
(Energy(kg m^2 s^(-2)))/(Time(s))
kg m2 s-3 (W)
Table 1.2
5.       Table 1.2 show a list of derived quantity and their respective derived units.
6.       For easier recording and comparison, very large or very small measurement of physical quantities are represented by prefixes as shown in Table 1.3 below.
Prefix
Symbol
Value
Standard form
10n where n is
Example
Tera
T
1 000 000 000 000
1012
12
Tetrameter (Tm)
Giga
G
1 000 000 000
109
9
Gigabyte (GB)
Mega
M
1 000 000
106
6
Megawatt (MW)
Kilo
K
1 000
103
3
Kilojoule (kJ)
Hecto
h
100
102
2
Hectometre (hm)
Deca
da
10
101
1
Decasecond (das)
Deci
d
0.1
10-1
-1
Decimetre (dm)
Centi
c
0.01
10-2
-2
Centimetre (cm)
Milli
m
0.001
10-3
-3
Milliampere (mA)
Micro
µ
0.000001
10-6
-6
Microsecond (µs)
Nano
n
0.000000001
10-9
-9
Nanometre (nm)
Pico
p
0.000000000001
10-12
-12
Picometre (pm)
Table 1.3

A x 10n

Where 1 < A < 10 and n = integer. The magnitude should always be rounded to 3 or 4 significant numbers/figures.
Conversion of Units
1m       = 100 cm (102 cm)                                          1 cm    = 0.01 m (10-2 m)
1m2      = 10 000 cm2 (104 cm2)                                 1 cm2   = 0.0001 m2 (10-4 m2)
1m3      = 1 000 000 cm3 (106 cm2)                            1 cm3   = 0.000001 m3 (10-6 m3)
1kg      = 1 000 g (103 g)                                             1 g       = 0.001 kg (10-3 kg)
1 hour  = 3 600 s (3.6x103 s)                                       1 s        = 1/3600 hour
1 km    = 1 000 m (103 m)                                           1 m      = 0.001 km (10-3 km)

Chapter 1 Form 4 - Tutorial 2 (Physics)

Measurement and Vernier Caliper
1.       We as a human frequently need to make measurements for physical quantities by using standard measuring instruments.

2.       There are two types of errors
a)       Systematic Errors
-Cumulative errors that can be corrected. Usually caused by the measuring instrument when it   does not start exactly from zero. To correct it, the following equation can be used
Actual Reading = Measuring – Zero Error

Example: Zero Error

b)   Random Errors
        -Errors due to natural error or wrong techniques of measurement. To minimise the error, the position ot the eye must be in line with the reading, and for the instrument which have a scale and a pointer like an ammeter, a mirror is placed behind the pointer to minimise the error.

        Example: Parallax Error

3.       A pair of Vernier Calipers can be used to measure the thickness, diameter of a wire and depth of a liquid. Below is the picture of how the Vernier Calipers looks like.








4.       The main scale is marked in divisions of 1mm, while the Vernier scale is marked in divisions of 0.1mm.
5.       We need to check for zero error in order to obtain the accurate readings.

Micrometer Screw Gauge
1.       The Micrometer Screw Gauge is used to measure very small thickness and diameters to the accuracy of 0.01mm.

2.       Below are some of the error while taking the reading of the Micrometer Screw Gauge and ways to correct it.
Accuracy And Precision (Consistency)
1.       Accuracy is the degree of a measuring instrument to record readings close to the actual values.
2.       Precision/Consistency is the degree of a measuring instrument to record the consistent readings for each measurement by the same way.
3.       Sensitivity is the degree of a measuring instrument to record the small change in its readings.
Accurancy
Precision/Consistency
Sensitivity
How close the readings taken are to the actual value
The consistency of the readings taken (less relative deviation)
The ability of a measuring a small apparatus to detect small changes of the physical quantity
To increase accurancy:
-          Use more sensitive equipment
-          Repeat reading taken
-          Avoid Parallax Errors
-          Avoid Zero Errors or end Edge Error
To increase Precision:
-          Use a magnifying glass when reading the scale
-          Avoid Parallax Error
To increase sensitivity (eg. Mercury thermometer)
-          Use thin glass bulb wall
-          Use a narrow capillary tube
-          Use a smaller bulb size

Experimental Errors
1.       The systematic error is the error that appears in one direction only. The measurement obtained is deviated either consistently too high (always positive) or too low (always negative) from the actual value.
2.       The sources of systematic error:
a.        Zero Error of measuring instruments
b.       Incorrectly Calibrated scale of measuring instruments
c.        Repeated Error in reaction time
d.       Wrong Assumption
3.       Random Error has non-constant size of error and is unpredictable. The distribution of reading is sometimes positive and sometimes negative from the actual value. The sources of random error:
a.        Parallax Error when reading a scale
b.       Changes in the surroundings such as the temperature or pressure.

4.       Random Error can be reduced by taking the mean value(average) of repeating measurements.

Chapter 2 Form 4 - Tutorial 1 (Physics)

Chapter 2: Forces and Motion – Form 4

1. Kinematics is a study of the motion of objects
2. Linear Motion is motion in straight line
3. Distance is a total length of the path travelled by the object. [SI unit is m]                                               {Distance is a Scalar Quantity}
4. Displacement is the distance travelled in a specific direction. [SI unit is m]                                      (the shortest distance from starting point and the ending point) {Displacement is a Vector Quantity}

5. Speed is the rate of change of distance. [SI unit is ms-1]
6. Velocity is the rate of change of displacement. [SI unit is ms-1]
7. Acceleration is the rate of change of velocity. [SI unit is ms-2]
8. Deceleration is the decreasing of velocity in a period of time. [SI unit is ms-2]




Equation of Linear Motion with Uniform Acceleration

The various equations of linear motion of an object with uniform acceleration are given as follows:
*memorize the first equation.
*the other 3 equations are given in the Formulae List


Tutorial 2 : Forces and Motion
Newton’s First Law of motion (Law of Inertia) states that every object will continue in its state of uniform velocity or at rest unless it is acted upon by an external force.

Inertia is the tendency of an object to remain at rest, or if moving with uniform velocity, to continue its motion in a straight line.

Mass is measurement for the amount of inertia. A body of greater mass will have a greater inertia. It has a greater tendency to maintain its state of motion.
Phenomena of inertia
It is more difficult to push a bucket filled with sand than an empty bucket because the bucket filled with sand has a greater inertia.
 The momentum is defined as the product of its mass (kg) and velocity (ms-1)

Momentum is a measure of motion.  It is a vector quantity (both direction and magnitude). Its direction is the same as the velocity and its unit is kg m s-1 or N s

Calculation in Collision System and Explosion
1. For elastic collision (Langgar Pisah)
         **Kinetic energy also conserve:
  

2.      For inelastic collision (Langgar Lekat)

3. For Explosion

Newton’s Second Law Motion states that the rate of change of momentum is directly proportional to applied force and acts in the direction of the force. F=ma
Force = Mass (kg) x Acceleration (ms-1)

A push is a push or a pull. It is a vector quantity (both direction and magnitude) and its SI unit is Newton (N).
If 2 force F1=F2. The blocks are either at rest or in uniform velocity since the forces are balanced or the resultant force is zero.

The gravitational field strength is defined as force per unit mass acting on the object. Gravitational field strength,  . The unit for gravitational field strength is N kg-1

Impulsive Force is the force acting on objects in collision or explosion.


Impulse is the product of force and time or the change of momentum. Ft = mv – mu . The SI unit for impulse is Ns or kg m s-1.

There are several safety features installed to a vehicle in order to reduce serious injury to the driver and passengers.
• Bumpers are installed at the front and rear parts of vehicle to lengthen the collision time and to             reduce the impulsive force.
• Front or rear part of a car can be crumpled easily in order to lengthen the collision time so as to             reduce the impulsive force during an accident.
• An air bag is installed inside the steering wheel of a vehicle. It will inflate just as the car                         decelerates during an accident. Hence, the head of the driver which surges forward can 
          be protected.
• Steering wheel of a car is made of material soft enough to lengthen the collision time and                       cushion the momentum impact of the driver’s head during an accident.
• Dashboard of a car is normally made of material soft enough to lengthen the collision time 
          when the head of the driver collides at it.
• Windscreen if a car is manufactured in such a way so that during accidents the pieces of the                   screen chips will not be scattered easily as to hurt the driver or passengers
• The tyre of a car should be broad and with friction grooves so as to control better the stability               and the change of momentum of the car
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