Equations

Question 1

What is the equation for thinking distance?

Answer 1

Thinking Distance = Reaction Time x Speed of the Car

Question 2

What are the SUVAT equations?

Answer 2

v=u+at
s=ut+1/2at²
s=vt-1/2at²
s=1/2(u+v)t
v²=u²+2as

Question 3

What equation relates force, mass and acceleration?

Answer 3

F = ma
Force (N) = Mass (kg) x Acceleration (ms-2)

Question 4

How is the weight of an object calculated?

Answer 4

W = mg
Weight (N) = Mass (kg) x Gravitational force (ms-2)

Question 5

How is the moment of a force determined?

Answer 5

M = Fd
Moment (Nm) = Force (N) x Perpendicular Distance of the Line of Action of Force from the Point of Rotation (m)

Question 6

How is torque calculated?

Answer 6

T = Fx
Torque (Nm) = Perpendicular Separation Between Forces (m) x One of the Forces (N)

Question 7

How is density calculated?

Answer 7

ρ = m/v
Density (kgm-3) = Mass (kg)/Volume (m3)

Question 8

How is pressure calculated?

Answer 8

P = F/A
Pressure (Pa or Nm-2) = Force (N)/Area (m2)

Question 9

What is the equation used to calculate the pressure exerted by a vertical column of liquid?

Answer 9

P = hρg
Pressure (Pa or Nm-2) = Height (m) x Density (kgm-3) x Acceleration by Free Fall (ms-2)

Question 10

What is an expression for calculating upthrust?

Answer 10

U = vρg
Upthrust (N) = Volume of Liquid Displaced (m3) x Density of Liquid (kgm-3) x Acceleration due to Gravity (ms-2)

Question 11

How is efficiency calculated?

Answer 11

Efficiency (%) = (useful output energy/total input energy) x 100

Question 12

How is power defined as an equation?

Answer 12

P = E/t
Power (W) = Work Done (J)/Time (s)

Question 13

What is an expression relating power and constant speed?

Answer 13

P = Fv
Power (W) = Force (N) x Constant Speed (ms-1)

Question 14

How is gravitational potential energy calculated?

Answer 14

GPE = mgh
GPE (J) = Mass (kg) x Gravitational Field Strength x Change in Height (m)

Question 15

How is kinetic energy calculated?

Answer 15

KE = 1/2mv²
KE (J) = 1/2 x Mass (kg) x Velocity² (ms-1)

Question 16

What equation related force applied to a spring and its extension?

Answer 16

F = kx
Force (N) = Force Constant (Nm-1) x Extension (m)

Question 17

What are the two equations that can be used to calculate elastic potential energy?

Answer 17

E = 1/2Fx
E = 1/2kx²

F = force (N)
k = force constant (Nm-1)
x = extension (m)

Question 18

What is the equation for tensile stress?

Answer 18

σ = F/A
Stress (Pa) = Force (N)/Cross-sectional Area (m2)

Question 19

What is the equation for tensile strain?

Answer 19

ε = x/l
Tensile Strain = Extension (m)/Original Length (m)

Question 20

What is the equation for Young Modulus?

Answer 20

E = σ/ε
Young Modulus (Pa or Nm-2) = Tensile Stress (Pa or Nm-2)/Tensile Strain

Question 21

What equation defines electric current?

Answer 21

I = Q/t
Current (A) = Change in Charge (C)/Change in Time (s)

Question 22

What is the equation relating electric current and number density?

Answer 22

I = Anev

I - current (A)
A - cross sectional area (m2)
n - number density (m3)
e - elementary charge
v - drift velocity (ms-1)

Question 23

What is the equation for potential difference?

Answer 23

V = E/Q
Potential difference (V) = Energy Transferred (J)/Charge (C)

Question 24

What is the equation for electromotive force?

Answer 24

ϵ = E/Q
E.m.f (V) = Energy Transferred (J)/Charge (C)

Question 25

How is resistance defined?

Answer 25

R = V/I
Resistance (Ω) = P.d (V)/Current (A)

Question 26

What is the equation used to calculate resistance from length, cross-sectional area and resistivity?

Answer 26

R = ρl/A
Resistance (Ω) = (Resistivity (Ωm) x length (m))/Cross-sectional Area (m2)

Question 27

What are three equations that can calculate electrical power?

Answer 27

1) P=VI
2) P=I²R
3) P=V²/R

Question 28

How can the energy transferred by an electrical component in a given time be calculated?

Answer 28

E = VIt
Energy Transferred (J) = P.d (V) x Current (I) x Time (S)

Question 29

What are 4 key equations for analysing electrical circuits?

Answer 29

I=Q/t
V= W/Q
P = VI
V = IR

Question 30

What is the relationship between e.m.f, terminal p.d and lost volts?

Answer 30

E.m.f = terminal p.d + lost volts.

Question 31

What equation relates e.m.f, current, and internal resistance?

Answer 31

ϵ = I (R+r)
E.m.f = Current (Resistance + Internal Resistance)

Question 32

State the potential divider equation.

Answer 32

V(out) = [R₂/(R₁ + R₂)] x V(in)

Question 33

What is the wave equation?

Answer 33

v = fλ
Wave speed (ms-1) = Frequency (Hz) x Wavelength (m)

Question 34

How can phase difference be calculated for two points separated by distance x on a wave?

Answer 34

ΔΦ = d/λ
Phase Difference (degrees/radians) = Distance (m)/Wavelength (m)

Question 35

How is the intensity of a wave calculated?

Answer 35

I = W/A
Intensity (Wm-2) = Radiant Power Passing Through Surface (W)/Cross Sectional Area (m2)

Question 36

How is refractive index calculated?

Answer 36

n = c/v
Refractive Index = Speed of Light Through Vacuum (ms-1)/Speed of Light Through Material (ms-1)

Question 37

State the law of refraction.

Answer 37

nsinθ = k

n = refractive index
θ = angle between normal and incident ray.
k = constant