Physics EOY

A physical quantity:

• can be measured

• has its own unit

• expressed as numerical value with a unit

Physical quantity Formula

Physical quantity = numerical value x unit

Physical quantities can be classified into

• base qualities

• derived qualities

Precision of an instrument

smallest unit that the instrument can measure

Base Quantities (7)

• Mass

• Length

• Time

• Electric Current

• Temperature

• Amount of Substance

• Luminous Intensity

SI Base Units (7)

• kilogram

• metre

• second

• ampere

• kelvin

• mole

• candela

Mass Base Unit

kg

Length Base Unit

m

Time Base Unit

s

Electric Current Base Unit

A

Temperature Base Unit

K

Amount of Substance Base Unit

mol

Luminous Intensity

cd

Derived Quantities (7)

• Force

• Pressure

• Work Done

• Power

• Electric Charge

• Electromotive Force

• Frequency

Define Derived Quantities

Quantities that are obtained with a formula that comprises operations of base quantities

Force Formula

F = Mass x Acceleration

Pressure Formula

P = Force/Area

Work Done Formula

Work = Force x Distance

Power Formula

Power = Work/Time

Electric Charge

Electric Charge = Current x Time

Force SI unit

Newton, N

Pressure SI unit

Pascal, Pa

Work SI unit

Joule, J

Power SI unit

Watt, W

Frequency SI unit

Hertz, Hz

Express unit of kinetic energy in terms of base units.

Prefixes

• Tera

• Giga

• Mega

• Kilo

• Deci

• Centi

• Milli

• Micro

• Nano

• Pico

To get more kisses, daddy cooks mommy more nice pancakes

Tera (T)

10¹²

Giga (G)

10⁹

Mega (M)

10⁶

Kilo (k)

10³

Deci (d)

10^-1

Centi (c)

10^-2

Milli (m)

10^-3

Micro (micro)

10^-6

Nano (n)

10^-9

Pico (p)

10^-12

Stuff I should know

• Unit Conversion

• Standard Form

• Estimation

Common instruments to measure length

• Tape Measure

• Metre Rule

• Calipers

• Digital Calipers

• Digital Micrometer Screw Gauge

Precision of metre rule

0.1 cm

Precision of tape measure

0.1 cm

Precision of digital calipers

0.01 mm

Precision of digital micrometer screw gauge

0.001 mm

Parts of a digital caliper

• Outside Jaws

• Inside Jaws

• Digital Display

• Zero Button

• Depth Rod or Tail

Parts of a digital micrometer screw gauge

• Anvil

• Spindle

• Thimble

• Ratchet

• Zero Button

Stop Watch Precision

0.01 seconds but only record 0.1

Define period of oscillation

Time taken by the pendulum to complete one oscillation

What is an oscillation

One full swing, back and forth

Period of oscillation is independent on:

• the mass of pendulum bob

• initial angle of displacement

Period formula

Total time/Number of oscillations

Define scalar quantities

• physical quantity which has magnitude only

• Scalar = magnitude, unit → speed = 10 ms^-1

Define vector quantities

• physical quantity that has both magnitude and direction

• Vector = magnitude, unit, direction → velocity = 10 ms^-1 due west 

Scalar quantity example

• distance

• speed

• mass

• energy

Vector quantity example

• displacement

• velocity

• weight

• acceleration

Define kinematics

• motion of a body or a system of bodies, without consideration of its mass or the forces which cause the motion

Define Distance

• total length travelled by a body regardless of the direction of motion

• Distance = scalar, metre (m)

Define displacement

• distance measured in a straight line in a specified direction

• Displacement = vector, metre (m)

Define speed

• body defined as the distance travelled per unit time

• 

• Speed = scalar, metre per second (m s^-1)

Define average speed

•  total distance travelled divided by the total time

Define instantaneous speed

•  speed of the body at any given point in time

Define velocity

• change in displacement per unit time

• 

• Velocity = vector, metre per second (m s^-1)

Define acceleration

• change in velocity per unit time

• Acceleration = vector, metre per second squared (m s^-2)

When does velocity change?

When a body accelerates, decelerates or changes direction

Define rectilinear motion

two possible directions for body to move, must be opposite

Displacement-Time Graph Uniform Velocity

Gradient Formula

• Change in y/Change in x

Gradient of a displacement-time graph is the ______

velocity

Describe motion of Uniform Velocity D-T Graph: Answer format

• velocity of object from t₁ to t₂ is constant at [velocity]

• direction (positive/negative)

displacement-time

constant velocity, positive

displacement-time

deceleration, positive

displacement-time

acceleration, positive

displacement-time

zero acceleration, zero velocity

displacement-time

acceleration, negative

displacement-time

deceleration, negative

When describing curves: Answer Format

• Sign of gradient of curve (positive, negative, zero)

• Changes in magnitude of gradient (increasing/acceleration, decreasing/deceleration, constant)

The gradient of a velocity-time graph is the _________

acceleration

Area under velocity-time graph is ____________

change in displacement

Example of Answer Format for Velocity Time

• From t = 0 to t = 5, the body is traveling with a constant acceleration at 3 ms-2. Direction of acceleration is in the positive direction, or velocity of the body increases proportionately with time from ms-1 to 15ms-1.

• From t = 5 to t = 10, the body is accelerating at a decreasing rate, reaching a velocity of 20 ms-1. Direction of acceleration is in the positive direction.

• From t = 10 to 1 = 15, the body is traveling at a constant velocity of 20 ms-1.

• From t = 15 to t = 20, the body is decelerating uniformly at 4ms2. The direction of acceleration is in the negative direction and body comes to a stop at t = 20s.

• From t = 20 to t = 25, the body is stationary.

• From t = 5 to t = 30s, the body is traveling with a constant acceleration at 2 ms-2. Direction of acceleration is in the positive direction.

• Finally, from t = 30 to t = 35, the body is decelerating at a decreasing rate. The direction of acceleration is in the negative direction and body comes to a stop at t = 35s.

Define a freely-falling body

• a body that moves under the influence of gravitational force of attraction only

• falls with a constant acceleration of 9.81 ms^-2

What is terminal velocity?

• body accelerate downwards → velocity increase

• velocity increase = air resistance increase → acceleration downwards decreases

• air resistance becomes equal to weight → net acceleration becomes zero

• body travels at uniform velocity = terminal velocity

Air resistance is _________ on velocity.

dependent

For the equations of motion to be valid, what conditions need to be fulfilled?

• acceleration is constant

• motion is rectilinear

Kinematic Equation Formulas

Define constant force and provide examples

• act when two objects have physical contact

1. applied

2. normal contact

3. frictional

4. elastic

5. viscous

Define non-constant force and provide examples

• act over a distance without physical contact between two objects

1. gravitational

2. magnetic

3. electric

non-contact forces are also called ____

field forces

Define gravitational field

• a region in which a mass experiences a force due to gravitational acceleration

Compare mass and weight

Define inertia

Inertia refers to the resistance of a body to resist a change in the state of rest or motion of the body.

Greater mass = _______ inertia

greater

Define normal contact force

• perpendicular force extended by the surface of one object on the surface of another when they are in physical contact and it prevents objects from passing through each other

Characteristics of the normal contact force (4)

• only exists when an object is in contact

• always perpendicular to contact surface and its direction is through object of interest

• normal force does not always pass through the CG of the object

• magnitude can change; not always equal to weight of object

When magnitude of normal contact is equal to weight, the object is said to be in __________

equilibrium

Define friction

• contact force that acts between objects that opposes or tends to oppose or resist motion

• always act opposite to direction of motion at point of contact

Characteristics of friction

• When contact surfaces are smooth → little to no friction

• When contact surfaces are rough → friction

• Parallel to surface

• Magnitude of friction is proportional the normal force

Viscous force is also called ___ and ____

drag, air resistance

Viscous force _____ with speed of the object and ____ with the surface area of the object.

increases, linearly

Greater speed = ___ viscous

larger

Greater surface area = _____ viscous force

larger

Viscous force depends on __________

nature of fluid