Physics Review

Question 1

Define displacement, velocity, speed, and acceleration.

In what units are they measured?

Answer 1

Displacement is the change in position (magnitude = net distance or distance from start to finish) in meters

Velocity is the rate of change of position = Change in position/ change in time

Speed is the magnitude of velocity (m/s)

Acceleration is the change in velocity over change in time (m/s²)

Question 2

State each of the big five kinematic equations.

Under what conditions can they be applied?

Answer 2

d = ½ (v_o + v)

v = v_o + at

v = v_ot + ½ at²

v_o = vt - ½ at²

v² = v_o² + 2ad

They can only be applied when acceleration is constant (uniform)

Question 3

Give the magnitude and direction of free fall-acceleration near the surface of the earth

Answer 3

Direction of g is downward (10 m/s²) toward the surface of earth, radially toward the center

Question 4

Define inertia. How is it measured? State Newton’s Law of Inertia

Answer 4

Inertia is an object’s natural resistance to change in its state of motion.

It is measured by mass in kg

F_net = 0 when velocity is constant

Question 5

State Newton’s second Law of Motion.

Define Net force. In what units is it expressed?

Answer 5

F_net = ma

where the net force = the sum of all forces acting on the object

Force is measured in Newtons

1 N = 1 kg*m/s²

Question 6

State Newton’s third law of motion

Answer 6

If object exerts a force on object 2, then obect 2 exerts an equal and opposite force back on object 1.

Question 7

Define weight.

Give at least two reasons why mass is different from weight

Answer 7

Weight is the gravitational force acting on an object. It varies with location and is measured in Newtons.

Mass is not a force and does not vary with location (eg. on Eath vs on the moon) and is measured in kg

Question 8

State Newton’s Law of Gravitation

Answer 8

Every pair of objects exerts a gravitational attraction on each other and its strength

F = GMm/r²,

Where G = is the universal gravitational constant (6.6 x 10^-11 m³/kg*s²)

r is the center of mass to center of mass

Question 9

Define normal force. Is the magnitude of the normal force on an object always equal to the objects weight?

Answer 9

F_N is the component of the contact force exerted by a surface that is perpendicular to the surface.

No, it is not

Question 10

Define friction and give the equation for the force of friction

Answer 10

friction is the component of the contact force exerted by a surface that is parallel to the surface

f_k = u_k* F_N

f_s(max) = u_s* F_N

Question 11

Define center of mass. How is it located?

Answer 11

The point where all object’s mass can be considered to be concentrated = point that behaves as if the object were a single particle = the balance point.

x_cm= (m₁x₁ + m₂x₂)/(m₁*m₂)

Question 12

Define uniform circular motion, centripetal acceleration, and centripetal force

Give the formulas of the magnitudes of centripetal acceleration and centripetal force.

What are their directions?

Answer 12

UCM = constant-speed motion in a circle

a_c= acceleration toward the center of a circle necessary to keep an object on a circular path without changing its speed.

a_c= v²/r

F_c = the net force necessary to cause centripetal acceleration

F_c = ma = mv²/r

Both point toward the center of the circle

Question 13

Give the equation for torque, lever arm, and rotational inertia

Answer 13

t = rFsin(theta) = I*F

t_net = Ia

Where I is the rotational inertia

The farther the mass is from the axis of rotation, the larger the rotational inertia

Arms tucked in = less resistance to turning = lower rotational intertia

Question 14

Define equilibrium

Answer 14

An object is in equilibrium if

F_net=0 and t_net = 0

Question 15

Define momentum. Is it a vector or scalar?

Define impulse. Is it a vector or scalar?

Answer 15

Linear momentum = mass x velocity

p = mv in kg*m/s

Impulse = force x change in time

J = F*t

Impulse and momentum are both fectors

Question 16

State the law of conservation of momentum

Answer 16

If not net external force acts, then total momentum is conserved in a collision between freely moving objects

Total p_before = total p_after

Since momentum is a vector, it is conserved in all directions

Question 17

Define elastic collision, inelastic collision, and perfectly inelastic collision

Answer 17

• Elastic collision* is when objects bounce off one another without deforming; kinetic energy is conserved
• Inelastic collision* involves deformation of the object; kinetic energy is not conserved

Momentum is conserved in both elastic and inelastic collisions*

Perfectly inelastic is when objects stick together after the collision

A perfectly elastic collision the greatest kinetic energy loss in a collision, as not only do they deform, they form a single object

Set the total momentum equal to the total mass times velocity

p_total = m_total x v

Question 18

Define work and give its units

Answer 18

Work is the force acting over displacement

W = Fd cos (theta)

Scalar, measured in Joules

1 J = 1 N*m

Question 19

Define power and give its units

Answer 19

Power = Work/time

Watts

1 W = 1 J/second

Question 20

Define kinetic energy and give its units.

Answer 20

Kinetic energy is the energy an object has by virtue of its motion

½ m*v²

Joules

1 J = 1 N*M

Question 21

Give the work energy theorem

Answer 21

W_total = Change in KE

Question 22

Gravitational potential energy.

Answer 22

PE_grav = mgh

Delta h > 0 if going up

Delta h < o if going down

Question 23

What is the equation for total mechanical energy? and the law of mechanical conservation of energy?

What is the work done by non-conservative forces?

Answer 23

E = KE + PE

KE₁ + PE₁ = KE₂ + PE₂

KE_I + PE_I + W_nc = KE_f + PE_f

Question 24

Define heat and temperature. How are they different?

Answer 24

Heat is the transfer of thermal (internal) energy between a system and its environment. An extensive property - depends on the mass of the material

Temperature is a measure of the average kinetic energy of molecules in a system. An intensive property - doesn’t depend on the amount of material

Answer 25

Conduction is heat transferred through contact Convection is heat transferred by moving masses of fluid Radiation is heat transferred by emission and absorption of electromagnetic waves or photons

Question 26

State the first Law of thermodynamics Define internal energy and work What are the sign conventions of heat and work?

Answer 26

Change in Energy **E = Q - W** Q = net heat transfer, W = net work Change in internal energy of a system depends on how much heat is transferred into or out of the system and the work done by or on the system W is the work done by the system. If the _gas expands_, W is _positive._ (System does positive work) If gas is _compressed_, W is _negative_ (Work is done on the system) If _heat is added to the system,_ Q is positive If _heat is removed from the system_, Q is negative

Question 27

Define isobaric, isochoric, isothermal, and adiabatic

Answer 27

**Isobaric** = constant pressure **W = Q - PΔV** **Isochoric** = constant volume **ΔE = Q** - Isochoric _processes do no work,_ all of the energy change is due to heat flow (Piston is locked in place with a stopper) **Isothermal** = constant temperature **Q = W** - (Ideal gas in a metal cylinder submerged in a water bath) **Adiabatic** = no heat is exchanged between the system and the environment **ΔE = -W** (insulated cylinder)

Question 28

State the second law of thermodynamics. Define entropy

Answer 28

Entropy of a _closed system stays the same or increases during any thermodynamic process_ (Heat cannot be completely converted to work) Entropy is a measure of the disorder of a system Increase in entropy (+ΔS) Decrease in entropy (-ΔS)

Question 29

# Define stress and strain. What are their units? How are they related?

Answer 29

**Stress =** **Force/Area** _Tensile or compressive stress_, force is **perpendicular** to area _Shear stress_, force is **parallel** to area Stress = N/m² **Strain =** **ΔL/L (**change in length over original length) Strain has no units *Stress is proportional to strain*

Question 30

# Define density and specific gravity. What are their units? What is the density of water?

Answer 30

Density = m/v Specific gravity = p_substance/p_water Density = kg/m³ Specific gravity has no units p_water = 1,000 kg/m³ = 1 g/cm³

Question 31

Buoyant force

Answer 31

Buoyant force = net upward force everted by a fluid F_b = weight of fluid displaced = p_fluid\*V_submerged\*g

Question 32

Pressure formula and units

Answer 32

Pressure = Force/Area 1 Pascal (Pa) = 1 N/m² 1 atm = 100 kPa or 10⁵ Pa

Question 33

Gauge pressure and hydrostatic gauge pressure

Answer 33

Gauge pressure = Total pressure - atmospheric pressure P_total = P_surface + P_gauge Hydrostatic gauge pressure is the pressure due to being immersed within a fluid (depends only on depth) P = p_fluid\*g\*d d = depth

Question 34

Define Pascals law

Answer 34

A pressure that is applied to the surface of a confined liquid is transmitted undiminished to every part of the fluid; all points have the same height and same pressure

Question 35

Flow rate Incompressible fluids

Answer 35

Flow rate f = Av (Cross-sectional area x flow speed) M³/s f₁=f₂ or A₁v₁ = A₂v₂

Question 36

Define ideal fluid flow

Answer 36

Ideal fluid flow occurs when the fluid is incompressible, has no viscosity, is laminar, and has a steady flow rate

Question 37

State Bernoulli's equation and the conditions they may be applied

Answer 37

For ideal fluid flow ## Footnote ![]()

Question 38

What is the electric charge on a proton and electron?

Answer 38

e+/e- = +/- 1.6 x 10^-19 C

Question 39

Equation for the electrostatic force between two point charges

Answer 39

Kqq/r² k = 9 x 10⁹ N\*m²/C²

Question 40

Define conductor and insulator

Answer 40

Conductor = electric charges (free electrons) can move easily Insulator = electric charges cannot move easily (rubber, wood, glass)

Question 41

Define electric field. How does the direction of the electric field depend on the sign of the source charge?

Answer 41

Electric field = electric force per unit charge Field lines point away from positive charges and toward negative charges Electric field strength: E = kQ/r² E = N/C or V/m

Question 42

Define electric potential and voltage and give their units

Answer 42

1 V = 1 J/C ## Footnote ![]()

Question 43

What is the relationship between electric field and electric force

Answer 43

The force on a charge at a position where the electric field is given by F = qE

Question 44

Current units and how does it flow

Answer 44

Current (I) = net charge flowing per unit time in Amps 1 A = 1 C/s Current flows in the direction of positive to negative

Question 45

Resistance

Answer 45

R = V/I 1 ohm = 1 V/A R = pL/A

Question 46

Voltage

Answer 46

V = IR R is independent of V or I

Question 47

Power lost by a resistor; what type of energy is this? Power supplied by a voltage source; what type of energy is this?

Answer 47

P = I²R = IV = V²/R; thermal energy P = IV; electrical energy

Question 48

What does an ammeter measure? Where should it be placed in a circuit? What is its ideal resistance? What does a voltmeter measure? Where should it be placed in a circuit? What is its ideal resistance? How are photoelectrons detected? Where do they travel?

Answer 48

An _ammeter_ measures **current** and should be placed **in series** with the compenent it is measuring. Its ideal resistance is 0. A _voltmeter_ measures **voltage** and should be placed in **parallel** with the component whose voltage it is measuring. Its ideal resistance is infinite. _Photoelectrons_ are detected by the **ammeter,** and wants to go to areas of **higher potential**, as they are electrons.

Question 49

Define capacitor, capacitance, and dieletric. In what units is capacitance measured?

Answer 49

Capacitor = two conductors (usually parallel plates) carrying equal but opposite charges Capacitance = charge/voltage **C = Q/V** C is in farads 1 F = 1 C/V Dielectric is an *insulator* between capacitor plates

Question 50

How strong is the electric field between the plates of a capacitor? How much energy is stored? What is the effect of a dielectric?

Answer 50

**E = V/d**, d is the distance between the plates PE_elec = ½ CV² A dielectric increases capacitance

Question 51

What generates a magnetic field? What are its units

Answer 51

A moving charge generated a magnetic field B = Tesla 1 T = 1 (N\*s)/C\*m)

Question 52

Equation for the magnetic force exerted on a charge What is the direction of this force?

Answer 52

F = q(v x B) Magnitude of force: F = qvBsin(theta) Force is perpendivular to velocity B obeys right hand rule - point thumb in the direction of the velocity \* = out of the plane/ x = into the plane Fingers point in the direction of the field (B) Palm points in the direction of F_b for positive charge / back of hand is for negative charge Force is always perpendicular to velocity and the field

Question 53

# Define simple harmonic motion, amplitude, period, and frequency What is the relationship between period and frequency?

Answer 53

**SHM** = Oscillatory motion, where _restoring force is proportional to displacement_ **Amplitude** is the maximum displacement from equilibrium **Period** = time required for the oscillator to complete one full cycle frequency = # cycles per unit time **f = 1/T** **Spring frequency; f = 1/2(pi) x (sq(k/m)**

Question 54

Give the equation for the force exerted by and elastic potential energy stores in a stretched or compressed spring

Answer 54

F = -kx PE_elastic = ½kx²

Question 55

What determines the frequency of a spring-block simple harmonic oscillator? Of a simple pendulum?

Answer 55

Mass of block and force constant of a spring f = ½ (3) k/m g and Length of a pendulum ½(3) g/L

Question 56

# Define transverse wave and longitudinal wave Define compression, and rarefaction

Answer 56

**Transverse wave:** oscillation of medium is **perpendicular** to the propagation of the wave **(sound waves/light)** **Longitudinal wave** - motion of medium is **parallel** to the propagation of the wave **Compression** = the region of _maximum pressure_ **Rarefaction** = the region of _minimum pressure_

Question 57

What is the relationship between wave speed, wavelength, and frequency?

Answer 57

wave speed = frequency x wavelength v = f\*lambda

Question 58

What determines wave speed? What determines the speed of a sound wave?

Answer 58

Properties of the medium (except when taking into account dispersion with light, where frequency matters to a small extent) Speed of sound is determined by the medium's resistance to compression v = (B/p)^½

Question 59

What will happen to a wave's frequency, speed, and wavelength when it enters a new medium?

Answer 59

Frequency remains unchanged velocity and wavelength will change proportionately

Question 60

Define standing wave, node, antinode, harmonic frequency, and harmonic wavelength

Answer 60

Standing wave = superposition of two oppositely-directed traveling waves that results in a single, non-traveling wave Node = point of zero displacement antinode = point of maximum displacement Harmonic frequency = common frequency of traveling waves that will produce a standing wave Harmonic wavelength = common. wavelength of traveling waves that will produce a standing wave

Question 61

How do you calculate sound intensity and how is sound level calculated from sound intensity?

Answer 61

Sound intensity I = Power/area Sound level B = 10 log (I/I_O) where I_o = 10^-12 W/m²= threshold of hearing

Question 62

Describe the Doppler Effect. What conditions would result in increased observed frequency? Decreased observed frequency?

Answer 62

The change in the observed frequency of an acoustive wave caused by relative motion of the source and detector Relative motion toward results in higher observed frequency Motion away results in a lower observed frequency

Question 63

Rank the colors of visible light in order from lowest to highest frequency

Answer 63

ROYGBV

Question 64

Define angle of incidence, angle of reflection, angle of refraction, and index of refraction

Answer 64

Angle_incidence = angle that the incident beam makes with the normal boundary Angle_reflect = angle that the reflected beam makes with normal to boundary Index of refraction: n = c / v v = speed of light through the medium under study

Question 65

Law of reflection and law of refraction

Answer 65

**Law of reflection** is for _mirrors:_ Angle of incidence = angle of reflection **Law of refraction** (Snell's Law) if for _lenses:_ n₁\*sin(theta) = n₂\*sin(theta)

Question 66

# Define total internal reflection When does it occur? How do light and sound change when they pass through water? Define diffraction

Answer 66

Total internal reflection occurs when the light strikes the boundary of a medium with a **lower refractive index (n₂ \< n₁)** at an angle of incidence greater than the critical angle _Light going from water to air_ **Sin theta_critical = (n₂/n₁)** Light gets *slower* in water, bending *toward* from the normal Sound gets faster in water, bending *away* from the normal **Diffraction** is the spreading out of waves when they encounter an obstacle or aperature.

Question 67

Equation for focal length How do the terms concave and convex relate to converging and diverging lenses?

Answer 67

Focal length: f = r/2 **Virtual images** form from **diverging optics** (concave lens/convex mirror) - i \< 0, f \> 0, m \> 0 and the image is _upright_ **Real images** form from **converging optics** (convex lens/concave mirror) - i \< 0, f \< 0, m \< 0 and the image is _inverted_

Question 68

Mirror lens equation Magnification equation

Answer 68

1/o + 1/i = 1/f m = -i/o o = object distance from mirror or lens i = image distance

Question 69

Real images and virtual images

Answer 69

Real image is formed by the actual convergence of light rays Real images are always inverted Virtual image is an image from which light only appears to diverge Virtual images are always upright

Question 70

Lens power equation Describe far-sightedness and nearsightedness

Answer 70

**P = 1/f** Hyperopia - far-sightedness Focal length of the lens system is too long, image forms behind the retina (Use a **converging** lens to fix) Myopia - near-sightedness; can see things that are close Focal length of the eye's lens system is too short, image forms in front of the retina (Use a **diverging** lens to fix) If not using a lens to fix; Strength of the eye lens (Which is a converging lens) **is positive**

Question 71

Equation for the maximum kinetic energy of an electron ejected as a result of the photoelectric effect Define work function and stopping potential

Answer 71

KE_max = hf - f = -eV_stop **Work function** f is the _minimum energy_ needed to dislodge a surface electron from a metal **Stopping potential** is the _minimum voltage_ required to prevent ejected electrons from reaching the detecer

Question 72

Heisberg uncertainty relation

Answer 72

**ΔxΔp≥ h/2π** **The better one knows the position of a particle, the less one knows amount the momentum and vice versa**

Question 73

Give the equation for stopping potential (V_stop)

Answer 73

KE_max = -eV_stop

Question 74

What properties do light and sound waves share? What can light do that sound cannot?

Answer 74

They both can reflect, refract, and diffract. They both have a speed of propagation (v = frequency \* wavelength) Light _can be polarized_ Light _can propagate without a medium,_ meaning that it can travel in a vacuum

Question 75

Give Kirchoff's Laws

Answer 75

1. Conjunction rule - currents into and out of any point in a circuit must equal each other. (Conservation of charge) Elements in **series** have **equal current** I₁ = I₂ + I₃ 2. Loop rule - sum of voltages arond any closed loop circuit must equal zero. (Conservation of energy) Elements in **parallel** have the **same voltage** +V_battery + (-V₁) + (-V₂) = 0