Bahasa Inggris Fisika
MODULE I
THE CONCEPT OF PHYSICAL QUANTITIES AND THEIR MEASUREMENTS
Measurement is an estimation of a magnitude of some attributes of an object, such as length, time or weight, relative to a unit of measurement.
Physical quantities are characterized by:
a number that describes the magnitude of the quantity,
a unit of measure, which describes the nature of the quantity,
a method to perform the measurement of the physical quantity.
A physical quantity is a physical property that can be quantified. This means it can be measured and/or calculated.
1. Length
expresses the distance or extent in space. The standard used for measurement is a distance light travels in vacuum for second
An object of the same length as the standard bar is said to have a length of l = 1 [m] "meter".
Mass expresses the quantity or amount of matter. The standard is a cylinder of platinum-iridium, and an object of same mass as the standard is said to have a mass of m = 1 [kg] "kilogram".
This is a rather abstract concept which necessitates a precise definition through a measurement procedure. The standard of time has changed with time, and now an atomic clock is used for this purpose
The value of a physical quantity
The value of a physical quantity Q is expressed as the product of a numerical value {Q} and a physical unit [Q]
Q = {Q} × [Q]
Units of measurement
Units are standards for measurement of physical quantities.
The International System is called the SI, using the first two initials of its French name Système International d'Unités.
EVALUATION
1. Multiple choice
2. Essay
Question 1
If a certain value of power is written as P = 42.3 × 103 W = 42.3 kW, then explain the value, unit, and the quantity of the power above.
Solution
P represents the physical quantity of power.
42.3 × 103 is the numerical value {P}.
k is the SI symbol for kilo, representing the value of 103.
Question 2
What is the dimension of acceleration and force.
Solution
The dimension of acceleration is
a = m/s2 = LT−2
The dimension of force can be obtained (derived) from Newton’s second law.
F = ma = kg m/s2 = MLT−2
Question 3
The Earth's mass is about 5,973,600,000,000,000,000,000,000 kg. Write the Earth’s mass in scientific notation
Solution
The Earth's mass is about 5,973,600,000,000,000,000,000,000 kg. In scientific notation, this is written 5.9736 × 1024 kg.
Question 4
The length, width, and thickness of the cube are 5.1 cm, 2.5 cm, and 2.1 cm. What is the
volume of the cube? (Use the significant number rule)
A. 26 cm3
B. 27 cm3
C. 26.8 cm3
D. 26.78 cm3
E. 26.775 cm3
MODULE 2
Kinematics of rectilinear motion
Mechanics:
Kinematics
is a branch of mechanics concerning with motions without regarding the causes of the motions
Dynamics
is a branch of mechanics concerning with motions with regarding the causes of the motions.
In physics, the object is called in motion if its position changes against a reference point.
Rectilinear motion is the motion with rectilinear path
The physical quantity of rectilinear motions
1. Displacement and distance
Displacement is a change of the object’s position at a certain time.
∆x = xfinal – xinitial
Distance is a length of the actual path travelled by the object during a motion.
|∆x| = |xfinal – xinitial|
Example 1.2
An object moves in a line with x axis direction. The initial position of the object is in zero point. The object moves 3 meters to the right direction. Then, the object moves 2 meters to the left direction. Determine the displacement and distance of the object.
Solution
Look at the picture below.
Displacement
∆x1 = 3 – 0 = 3 m
∆x2 = 1 – 3 = -2 m
∆x = ∆x1 + ∆x2 = 3 + (-2) = 1 m
The direction is x positive.
Thus, the displacement of the object is 1 m with direction to the x axis positive.
Distance
| ∆x1 | = |3 – 0| = 3 m
| ∆x2 | = |1 – 3| = 2 m
| ∆x| = |∆x1 | + |∆x2| = 3 + 2 = 5 m
Thus, the distance of the object is 5 m.
2. Velocity and speed
Speed is the distance travelled by an object per unit of time. Velocity is the displacement of an object per unit per time. Speed is a scalar quantity and velocity is a vector quantity.
Velocity:
Average speed and average velocity
Instantaneous speed and instantaneous velocity
Exploration 2.2
Do you know the speedometer? Speedometer is the instrument to measure the instantaneous speed of an object like a motorcycle or a car.
Pay attention to the speedometer when a motorcycle or a car moves. Then, answer the questions below.
1. What is the unit of speed which you find in a motorcycle or car?
______________________________
2. Where will the hand of the speedometer moves, while a motorcycle or a car moves faster than before? (to the left or to the right)
______________________________
Acceleration
is a change of velocity per unit of time. Acceleration is a vector quantity. The symbol of acceleration is α.
Acceleration:
Average acceleration
Instantaneous acceleration
Kinds of rectilinear motion
1. Uniform rectilinear motion
is the motion in linear path with a constant velocity or speed.
2. Uniformly accelerated rectilinear motion
is a motion in a linear path with a constant acceleration.
The other equations in uniformly accelerated rectilinear motion
v = vo + at
Vertical motion
Is a kind of uniformly accelerated rectilinear motion in vertical direction.
1. Upward vertical motion
2. Downward vertical motion
3. Free fall motion
MODUL 3
Circular Motion
Circular motion is an object’s motion in circular path
1. Angular distance or angular displacement
Is the distance or displacement of particle in circular motion
2. Angular speed or velocity
is a speed or velocity in circular motion.
Two kind of angular speed or velocity:
Average angular speed or velocity
Instantaneous angular speed or velocity
3. Period and Frequency
The period is the time required by an object (particle) to reach a complete rotation.
It means that the period is the time required by an object to move from one point (suppose A) passes through a circular path which has radius R and back to the point (suppose A).
The frequency The relationship of period and frequency
The relationship of period and frequency
Angular speed or velocity:
Frequency
period
Linear speed
4.Acceleration in circular motion
a. Angular acceleration (α)
b. Tangential acceleration (αt)
c. Centripetal acceleration (αs)
The relationship of angular acceleration, tangential acceleration, and centripetal acceleration
Kinds of circular motion
1. Uniform circular motion
is a motion of object at circular path with constant angular velocity (ω = constant).
2. Uniformly accelerated circular motion
is the motion of an object at circular path with constant angular acceleration (α = constant).
The uniformly accelerated circular motion is analogue to the uniformly accelerated rectilinear motion
The uniformly accelerated rectilinear motion
The uniformly accelerated circular motion
v = vo + at
ω = ω0 + αt
x = x0 + v0t + ½at2
θ = θ0 + ω0t + ½αt2
v2 = v02 + 2ax
ω2 = ω02 + 2αθ
Example
A particle is at the edge of a wheel which moves in circular with constant angular velocity of 900 rpm. If the radius of the circle is 10 cm, determine:
a. the angular velocity in rad/s;
b. the centripetal acceleration.
Solution
ω = 900 rpm =
Thus, the angular velocity of the particle is 30π rad/s.
αs =
Thus, the centripetal acceleration of the particle is 90π2 rad/s2.
