Equations

Question 1

Speed / velocity

Answer 1

Speed= ditance/time
m/s m s

Question 2

Acceleration

Answer 2

a=change in velocity / change in time
m/s2 m/s s

Question 3

Gravitational field strength

Answer 3

g.f.s. = weight / mass
N/kg

Question 4

Density

Answer 4

Density = Mass / Volume
Kg/m3

Question 5

Resultant force

Answer 5

F= change in momentum / change in time
N. Kg m/s

Question 6

Spring constant

Answer 6

K = force(load) / extension
N/cm

Question 7

Moment

Answer 7

m = force x distnce (perpendicular from pivot)
Nm

Question 8

Momentum

Answer 8

p= mass x velocity
Kg m/s

force is needed to change momentum

Question 9

Force

Answer 9

Mass x acceleration

Question 10

Weight

Answer 10

Weight = mass x g.f.s
N. Kg. 9.8

Question 11

Energy

Answer 11

E = 0.5 x m x v2
J

Question 12

Change in gpe

Answer 12

🔼g.p.e. = mass x gravitational field strength x 🔼 in height
J/Nm Kg. N/Kg. m

Question 13

Work Done

Answer 13

Work done = force x distance
J

Question 14

Power

Answer 14

Power = work done / time
W or J/s. J. s.

electrical energy = power x time

Question 15

Efficiency

Answer 15

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

Efficiency = (useful power output / useful power input) x 100

Question 16

Mass

Answer 16

Mass = volume x density
Kg. m3. Kg/m3
g. cm3. g/cm3

Question 17

Pressure in solids

Answer 17

Pressure = force / area
Pa or N/m2. N. m2

Question 18

Pressure in liquids

Answer 18

p= height x density x g.f.s
Pa. m. kg/m2. N/kg

Question 19

Hooke’s Law springs

Answer 19

Force = k x X
K= constant N/cm
X= extension cm

Question 20

Impulse

Answer 20

Change in momentum= mv - mu. V= final velocity U= initial velocity m= mass
Kg m/s
-depending on direction
Ft=Force x time (Ns)

Question 21

Specific Heat Capacity

Answer 21

🔼Energy = mass x SHC x 🔼temperature
J. Kg. J/kg°C. °C.

Question 22

Boyle’s law (relationship between volume and pressure)

Answer 22

Initial pressure x initial volume = final pressure x final volume
Pressure –> Pa
Volume –> m3

Question 23

Velocity for free fall

Answer 23

Velocity = acceleration of gravity (9.8) x time

(Falling objects)

Question 24

2 formulas forRefractive index

Answer 24

1) n = sin(i) / sin(r)
i= angle of incident (air/vacuum)
r= angle of refraction (material)
n= refractive index (of material)

2) n = speed of light in air or vacuum/ speed of light in medium

Question 25

Time in waves(period)

Answer 25

Time= 1/frequency

Question 26

Frequency in waves

Answer 26

Freq= 1/ time

Question 27

Speed/velocity of wave (2)

Answer 27

wave speed (m/s) = frequency (Hz) × wavelength (m) ( v = f x λ)

Speed = wave length/period (s = d/t)

Question 28

Critical angle

Answer 28

Sin(critical angle) = 1 / refractive index
or n = 1 / sin(c)

Question 29

Equation for current (2)

Answer 29

I = Q / t
I = V / R

Question 30

Potential difference (2)

Answer 30

1) V = I x R
2) V = W / Q (pd= work done / charge) work done is the same as energy transferred

Question 31

Resistance

Answer 31

V = I x R
voltage = current x resistance
Volts = Amps x ohms

Question 32

Power in circuits (3)

Answer 32

1)P = I x V
2)P= I² x R
3)P= V² / R

Question 33

Electrical Energy (2)

Answer 33

E= P x t
E= I x V x t

Question 34

E.m.f

Answer 34

e = W / Q
E.m.f = work done / charge

Question 35

Formula to calculate energy transferred by devince in kWh

Answer 35

Energy transferred (kWh) = Power (kW) x Time (h)

Question 36

Formula to calculate cost of appliance w/ price per kWh

Answer 36

Cost (p) = Energy transferred (kWh) x Price per kWh (p per kWh)

Question 37

2 resistors used in a potential divider

Answer 37

R1/R2=V1/V2