SUMMARY: GRADE 11 PHYSICS

UNIT 1: MOTIONCONCEPTS AND EQUATIONS SUMMARY

1. Uniform motion is motion at a constant velocity.

• Vectors and scalars• Distance and displacement• Position-time graphs• Average speed and velocity• Instantaneous velocity• Velocity-time graphs

v⃗av=Δ d⃗Δ t⃗

• Motion is a change in position relative to a given frame of reference.

• Distance is the length of the actual path travelled. It is a scalar quantity.

• Displacement is the length of the straight line between the initial and final positions. It is a vector quantity.

• Average speed is distance covered per unit time and average velocity is displacement per unit time.

• The sign of velocity gives the direction of motion. • A position-time graph for an object moving at a constant

velocity is a straight line with a non-zero slope. • Motion at a constant velocity is called uniform motion. • The slope of a straight line position-time graph gives the

velocity. The slope of the tangent at a point on a curved position-time graph is the instantaneous velocity. The slope of the line connecting the first and last points is the average velocity.

• The area under a velocity-time graph represents the displacement; the slope represents the acceleration.

2. Acceleration is the rate of change in the velocity of an object.

• Acceleration• Equations of motion

a⃗=v⃗2− v⃗1

Δ t

v2+v1

2=Δ d

Δ t

Δ d=v1Δ t+12

a Δ t 2

Δ d=v2 Δ t−12

a Δ t 2

v22=v1

2+2a Δd

• Acceleration is defined as the rate of change in velocity, and the change may affect the magnitude, direction, or both. Acceleration is a vector quantity. • The same signs for velocity and acceleration mean the

object is speeding up. Opposite signs for velocity and acceleration mean the object is slowing down.

• The position-time graph for an object undergoing uniformly accelerated motion is a curve. The corresponding velocity-time graph is a straight line with non-zero slope. The corresponding acceleration-time graph is a horizontal line.

• When solving problems in kinematics, choose the equation that contains the one unknown and three unknown variables.

Summary: Grade 11 Physics Page 1

UNIT 2: FORCESKEY CONCEPTS SUMMARY

3. Gravity is a universal force.

• Fundamental forces• Weight/gravitational force• Newton’s law of universal gravitation• Free fall• Projectile motion

F g=mg or F G=Gm1 m2

r2

Δ d x=v x Δ t

Δ d y=v1 y Δ t−12

g Δ t 2

• There are four fundamental forces: gravitational, electromagnetic, and strong and weak nuclear forces. All are action-at-a-distance forces.

• The weight of an object is the gravitational force acting on it.• Gravitational field strength g is the ratio of gravitational force

to mass at a specific location. The units of gravitational field strength are N/kg or m/s2.

• Newton’s law of universal gravitation states that the gravitational force of attraction between any two masses is directly proportional to the product of the masses and inversely proportional to the square of the separation distance between the centres of both masses.

• Free fall is the condition in which the only force acting on an object is the gravitational force. An object in free fall is a projectile and the path of the projectile is its trajectory.

• An object in free fall will feel weightless because there will be no contact force such as the normal force acting on it.

4. Forces can change the velocity of an object.

• Force• Net force• Newton’s laws of motion• Normal force• Friction• Factors affecting friction

F⃗ net=ma⃗

F fr=μF N

• Force is a push or a pull on an object. Force is a vector quantity measured in Newtons (1 N = 1 kg∙m/s2).

• Net force is the vector sum of two or more forces acting simultaneously on an object. A free-body diagram helps determine the net force acting on an object.

• Newton’s 1st law states that an object will continue being at rest or moving at constant speed in a straight line unless acted upon by a non-zero net force.

• Newton’s 2nd law states that when a non-zero net force acts on an object, the object accelerates in the direction of the net force. The magnitude of the acceleration is directly proportional to the magnitude of the net force and inversely proportional to the mass of the object.

• Newton’s 3rd law states that if object A exerts a force on object B, then B exerts a force on A that is equal in magnitude and opposite in direction.

• The normal force is the force two surfaces in contact exert on each other, perpendicular to the surfaces.

• Friction is a force that opposes either the motion of an object or the direction the object would be moving in if there were no friction. Static friction is present when an object is stationary but experiences an applied force. Kinetic friction is present when an object is moving.

• The magnitude of the force of kinetic friction acting on an object is directly proportional to the normal force on the object.

• The coefficient of friction is a proportionality constant that relates the magnitude of the force of friction to the magnitude of the normal force and is determined by the properties of the surfaces in contact.

Summary: Grade 11 Physics Page 2

UNIT 3: ENERGY AND SOCIETYKEY CONCEPTS SUMMARY

5. Energy is transferred and transformed by forces doing work.

• Work• Kinetic energy• Gravitational potential energy• Conservation of mechanical energy• Power• Efficiency

W=Δ E=F Δd cosθ

Ek=12

mv2

E g=mg h

P= WΔ t

efficiency=Eout

E in=

Pout

P in

E=mc2

• There are many forms of energy. Energy may be transformed from one form to another or transferred from one system to another but may not be created or destroyed.

• The SI unit of energy is the Joule (1 J = 1 kg∙m2/s2), but energy is also commonly measured in calories and kWh.

• Work is the change in energy of a system and is done when a force acts over a distance in line with the motion. Work is a scalar.

• Frictional forces do negative work on a system, reducing its total mechanical energy.

• The mechanical energy of a system is the sum of the kinetic energy and potential energy in the system.

• Hydroelectric plants transform the gravitational potential energy of falling water into the mechanical energy that turns turbines attached to generators.

• Power is the rate of energy transfer. • Machines are not 100% efficient, because of energy losses,

usually in the form of heat. • Nuclear energy is energy stored in the binding of the

particles of the nucleus and may be released by nuclear decay, fission, or fusion.

6. Thermal energy transfer conserves energy and obeys the Laws of Thermodynamics.

• Thermal energy• Specific heat capacity• Heat exchange• Latent heat of fusion and of

vaporization

Q=mcΔT

Qlost=Q gained

Q f =m L f and Qv=m Lv

• Thermal energy is the total kinetic and potential energy of the particles within an object.

• Heat is the energy transferred from a warmer object to a cooler object.

• The energy lost from the warmer object is equal to the energy gained by the cooler object, which illustrates the law of conservation of energy.

• Thermal energy can be transferred by conduction, convection, and/or radiation.

• The temperature of a substance is the average kinetic energy of its particles.

• The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 kg of the substance by 1 K, or 1°C.

• A change of state, or phase transition, occurs when energy is transferred to or from a substance at its boiling or melting point. Latent heat is the energy that is needed for a phase change. Temperature remains constant during a phase change.

• Fossil-fuel and nuclear thermal power plants use steam to drive turbines to generate electricity.

Summary: Grade 11 Physics Page 3

UNIT 4: WAVES AND SOUNDKEY CONCEPTS CHAPTER SUMMARY

7. Waves transmit energy.

• Longitudinal and transverse waves• Amplitude and intensity• Wavelength• Period, frequency• Universal wave equation• Wave reflection• Standing waves• Resonance

f = 1T

v=λ f

• In a transverse wave, particles are displaced perpendicular to the direction of the propagation. • In a longitudinal or pressure wave, particles are displaced

parallel to the direction of propagation, resulting in rarefactions and compressions.

• The positions of maximum displacement from equilibrium are crests and troughs. The amplitude is the distance from equilibrium to a maximum. Waves with a larger amplitude carry more energy.

• The wavelength of a wave is the length for one complete cycle, between one crest and the next. The period of a wave is the time for one complete cycle.

• The frequency of a wave is the inverse of the period, the number of oscillations per second, measured in Hertz.

• The speed of a wave depends on the properties of the medium.

• Waves reflect at the interface of two media.• When two waves interfere, the resulting pattern is the linear

superposition of the two waves. Constructive interference occurs when the amplitude is increased, destructive when the amplitude is decreased.

• When a wave interferes with its own reflection, it can create a standing wave pattern of nodes and antinodes.

• Standing waves can occur when an object is forced to vibrate at its natural or resonant frequency. The amplitude will increase if the forcing continues.

8. Sound is a longitudinal mechanical wave.

• Speed of sound• Frequency range of hearing• Sound intensity• Musical harmonics• Beats• Doppler effect• Sonic boom

v=332 ms0.6 m

s/oC T

f obs=vsound f source

vsound ±v source

• Sound waves travel faster in warm air than in cold air and even faster in liquids and solids.

• The human ear can distinguish frequencies, or pitches, between 20 Hz and 20 kHz. Frequencies below this range are infrasound, frequencies above are ultrasound.

• Sound intensity, which is heard as volume, is a measure of power per unit area over which the wave is distributed. Because of the logarithmic response of the human ear, intensity is often given by the decibel scale.

• Objects can vibrate at multiple resonant frequencies above the fundamental. These are called harmonics.

• Frequencies will sound musical together if the ratio between them is a small, whole number ratio. If two frequencies are very close to each other, beats will be heard.

• If an source is moving toward a listener, the apparent frequency will be increased. If the source is moving away, the apparent frequency will be decreased.

• An object travelling faster than the speed of sound will create a cone of increased-amplitude compressions that will be heard as a sonic boom when it meets the ear.

Summary: Grade 11 Physics Page 4

UNIT 5: ELECTRICITY AND MAGNETISMKEY CONCEPTS SUMMARY

9. The principles of conservation of energy and charge apply to electrical circuits.

• Conventional current and electron flow• Current, electrical potential difference, and resistance• Kirchhoff’s current and voltage laws• Series, parallel, and mixed circuits• Power and power consumption

I= Q t

V =EQ

V =IR P=VI

Req=R1R2. . .

1Req

= 1R1

1R2

.. .

• Current is the rate of flow of electric charge and is measured in Amperes. The direction of conventional current is opposite that of the electron flow.

• Potential difference, or voltage, is energy carried per unit charge and is measured in Volts.

• An electrical circuit contains an energy source, conductors, and a load to consume the energy from the source.

• The relationship between current, potential difference, and resistance in a circuit is described by Ohm's law.

• Kirchhoff’s current law states that the current entering a junction must be equal to the current leaving the junction.

• Kirchhoff’s voltage law states that in any closed circuit loop, the sum of the potential differences through all the components must be zero.

• In a series circuit, the current is constant, the total resistance is the sum of the resistors, and the total voltage of the battery equals the sum of the voltage drops across the resistors.

• In a parallel circuit, the total current equals the sum of the currents through each branch, the total resistance decreases as the number of branches increases, and the voltage is constant across each branch.

10. Current electricity produces magnetic fields.

• Characteristics and properties of magnetic fields

• Oersted’s principle• Right-hand rules• The motor principle• Faraday’s law of induction• Generators• Step-up and step-down transformers

• The law of magnetism states that like magnetic poles repel each other and unlike poles attract each other.

• A magnetic field is the three-dimensional region around a magnet in which magnetic forces are exerted.

• Oersted’s principle states that when a current moves through a conductor, it creates a magnetic field.

• The motor principle states that a current-carrying conductor will experience a magnetic force as long as the conductor is not parallel to the magnetic field.

• The factors that affect the strength of the magnetic force are the current, the magnetic field, and the length and orientation of the conducting wire.

• Faraday’s law of electromagnetic induction states that a changing magnetic field in the region of a closed-loop conductor will induce an electric current.

• A motor converts electrical energy to mechanical energy and a generator converts mechanical energy to electrical energy.

• A transformer can step up (increase) or step down (decrease) voltage.

Summary: Grade 11 Physics Page 5