Physics Textbook Flashcards

Question

What are the 2 equations that let you calculate the magnitude of centripetal acceleration?

Answer 1

a_c = v² / r a_c = r ω²

Answer 2

a_t = r α ## Footnote a_t = tangential acceleration r = radius α = angular acceleration

Answer 3

i represents the unit vector in the x direction (it is 1 unit long). j represents the unit vector in the y direction (it is 1 unit long).

Answer 4

Power = Work / Time

Answer 5

v = r ω ## Footnote v is the linear velocity ω is the angular velocity r is the radius (length from center to point where v is being measured)

Answer 6

W_net = ½mv_f² − ½mv_i² ## Footnote The net work done is equal to the change in kinetic energy.

Answer 7

1 W = 1 J / sec The Watt is a unit of power.

Answer 8

I = ∑mr² ## Footnote Moment of inertia (I) is the sum of mr² for all the point masses that it is composed of. I is analogous to m in translational motion.

Answer 9

F=ma F and a are vector quantities, so they have arrows over the letters.

Answer 10

Normal force = the force that acts on a resting object, which acts perpendicular to the surface that the object is resting on. Example = if a block is resting on a ramp, the normal force points in a direction perpendicular to the ramp, NOT straight up.

Answer 11

The two objects that have collided are **not** stuck together, but some deformation / loss of energy has occurred. Momentum **is** conserved. Kinetic energy **is not** conserved.

Answer 12

If the soup is very thick, the can will **not** roll as quickly as a can that has thinner soup, **even if the total masses are equal.** This is because the **thick soup** **rotates** inside the can (it gains translational **and** rotational KE), but the **thin soup does not rotate** inside the can (it gains translational KE **only**). PE_grav = KE_trans + KE_rot

Answer 13

The work done to displace the spring.

Answer 14

F_net = 0 τ_{net, external} = 0 The net force must be zero, and the net external torque must be zero.

Answer 15

PE_s = ½ k x² ## Footnote k is the spring's force constant x is the displacement of the spring from its resting position

Answer 16

F₁ / A₁ = F₂ / A₂

Answer 17

Alveolar walls of emphysema victims deteriorate, and the sacs combine to form larger sacs. Because pressure produced by surface tension decreases with increasing radius, these larger sacs produce smaller pressure, reducing the ability of emphysema victims to exhale. A common test for emphysema is to measure the pressure and volume of air that can be exhaled.

Answer 18

Frac. subm. = ρ_obj / ρ_fluid ## Footnote ρ_obj = avg density of object ρ_fluid = density of fluid

Answer 19

The ratio of change in length to length (ΔL/L₀) is defined as strain (a unitless quantity).

Answer 20

(Stress) = (Y) x (Strain) This is just a rearrangement of the main equation for the stretching of a rope under tension.

Answer 21

(P + ½ρv² + ρgh) Q = power ## Footnote Q = flow rate Multiply Bernoulli's equation by flow rate, and you get power.

Answer 22

It is a **fictitious force,** that "pushes" objects toward the outside (example = centrifuges). In reality, there is no force that does this.

Answer 23

2π rad = 1 revolution

Answer 24

γ = F / L ## Footnote Surface tension γ is defined to be the force F per unit length L exerted by a stretched liquid membrane.

Answer 25

P₁+ ½ρv₁²+ ρgh₁= P₂+ ½ρv₂²+ ρgh₂

Answer 26

The ratio of force to area (F/A) is defined as stress measured in N/m².

Answer 27

Objects at rest tend to stay at rest, and objects in motion tend to stay in motion, unless acted upon by an **unbalanced** outside force.

Answer 28

ΔL = (FL₀) / (AY) ΔL = change in length F = applied force of tension L₀ = initial length A = cross-sectional area Y = Young's modulus (elastic modulus), a unique constant for each material

Answer 29

N_R = (2ρvr) / η ρ = density of fluid v = speed of fluid r = radius of tube η = viscosity N_R \< 2,000 = Laminar flow N_R \> 3,000 = Turbulent flow

Answer 30

A system is in **unstable** equilibrium if, when displaced, it experiences a net force or torque in the **same** direction as the displacement from equilibrium. Example = a ball at the top of a hill.

Answer 31

Q = (πΔPr⁴) / (8ηl) ## Footnote Q = flow rate ΔP = difference in pressure r = radius η = viscosity l = length

Answer 32

The net external force on the system must be zero.

Answer 33

T² = ( 4π²r³) / ( GM )

Answer 34

A system is said to be in **stable** equilibrium if, when displaced from equilibrium, it experiences a net force or torque in a direction **opposite** to the direction of the displacement. Example = a marble at the bottom of a bowl.

Answer 35

1 J = 1 N m

Answer 36

An inertial reference frame is one in which the body has no net forces acting on it, and thus is not accelerating. Earth can **almost** be considered an inertial reference frame (exception: Coriolis Force). A non-inertial reference frame is one in which the body is experieincing acceleration. This can cause objects within the frame to experience **fictitious forces.** Examples: being in a turning car, centrifuges, merry-go-rounds, etc.

Answer 37

v_f² = v_i² + 2aΔx

Answer 38

It is a force that only depends on the initial and final positions of the mass, but NOT on the path taken. Conservative forces conserve mechanical energy. Non-conservative forces do NOT conserve mechanical energy. Examples of conservative forces: Gravity, springs. Examples of non-conservative forces: Friction, drag.

Answer 39

T_A² / T_B² = r_A³ / r_B³ ## Footnote The ratio of the squares of the periods (T_A and T_B) of any two planets about the Sun is equal to the ratio of the cubes of their average distances from the Sun (r_A and r_B).

Answer 40

Impulse = change in momentum Δp = F_netΔt

Answer 41

X_CG = (m₁x₁ + m₂x₂ + ...) / (m₁ + m₂ + ...) In other words, multiply each mass by its position, add them all up, and then divide by the total mass.

Answer 42

W_net = Iαθ ## Footnote I = moment of inertia

Answer 43

τ = r F sin(θ) τ = torque (Greek letter tau) r = distance from pivot point to point where force is applied F = magnitude of force applied θ = angle between the force and the vector directed from the point of application to the pivot point (θ=90° if perpendicular)

Answer 44

µ_K = ║F_f║ / ║F_N║ The force of kinetic friction = the magnitude of the force of friction / the magnitude of the normal force

Answer 45

Stable, unstable, and neutral.

Answer 46

L = Iω ## Footnote I = moment of inertia

Answer 47

Distance travelled.

Answer 48

1 hp = 746 Watts

Answer 49

F = (G M₁M₂) / r² ## Footnote G = Gravitational constant (6.67 x 10^-11 N m² / kg²) M₁ and M₂ = masses of the objects (in kg) r = distance between objects (in meters)

Answer 50

F_D = ½CρAv² ## Footnote C = the drag coefficient (a unique constant for each object) ρ = the density of the fluid A = the cross-sectional area of the object v² = velocity² (relative to the flow of the fluid)

Answer 51

Vectors have a magnitude AND a direction. Scalars have a magnitude ONLY, but NO direction.

Answer 52

τ_net = αI

Answer 53

Any net force that causes uniform circular motion.

Answer 54

ω = (Δθ) / (Δt) Angular velocity is the rate of change of an angle.

Answer 55

Every force must be opposed by an equal and opposite force.

Answer 56

P = ρgh ## Footnote ρ = density of the fluid g = acceleration due to gravity h = depth

Answer 57

A change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container.

Answer 58

The two objects that have collided are now **stuck together.** Momentum **is** conserved. Kinetic energy **is not** conserved.

Answer 59

Laminar flow is characterized by smooth flow of fluid in layers that do not mix.

Answer 60

Radians are unitless (they are defined as a ratio of distance).

Answer 61

A₁v₁ = A₂v₂ ## Footnote _{A = cross-sectional area of pipe/tube} _{v = velocity of fluid}

Answer 62

The twisting of an object, due to an applied torque.

Answer 63

KE_rot = ½ I ω² ## Footnote I = moment of inertia.

Answer 64

It is the acceleration of an object in uniform circular motion (due to a net force that acts inwards).

Answer 65

F_B = w_fluid ## Footnote The buoyant force (F_B) is equal to the weight of the fluid displaced by the object (w_fluid).

Answer 66

It is a unit of pressure. 1 Pa = 1 N / m²

Answer 67

F_net = Δp / Δt

Answer 68

τ = mr²α

Answer 69

G = (6.67 x 10^-11 N m² / kg²)

Answer 70

The two objects that have collided bounce off of each other with **no loss of energy.** In real life, only subatomic particles can achieve a perfectly elastic collision, but some everyday things come pretty close (example = pool balls). Momentum **is** conserved. Kinetic energy **is** conserved.