# OCR Gateway GCSE physics equations

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#1
Can anyone suggest any acronyms for the following equations?:

P = V x I. Power = Voltage x Current.

V = I x R. Voltage = Current x Resistance.

Q = I x t. Charge = Current x time.

E = V x Q. Energy = Voltage x Charge.

VP x IP = VS x IS.
Primary voltage x Primary current = Secondary voltage x Secondary current.

GPE = mgh. Gravitational Potential Energy = mass x gravity x height.

KE = ½mv2. Kinetic Energy = 0·5 x mass x velocity2.

W = F x d. Work done = Force x distance.

W = E. Work done = Energy transferred.

s = d ÷ t. speed = distance ÷ time.

a = (v-u) ÷ t. acceleration = change in velocity ÷ time.

F = m x a. Force = mass x acceleration.

w = m x g. weight = mass x gravity.

p = m x v. momentum = mass x velocity.

mv - mu = F x t. change in momentum = Force x time.

p = F ÷ a. pressure = Force ÷ area.

d = m ÷ v. density = mass ÷ volume.

v = f x λ. wave speed = frequency x wavelength.
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4 years ago
#2
(Original post by internet monster)
Can anyone suggest any acronyms for the following equations?:

P = V x I. Power = Voltage x Current.

V = I x R. Voltage = Current x Resistance.

Q = I x t. Charge = Current x time.

E = V x Q. Energy = Voltage x Charge.

VP x IP = VS x IS.
Primary voltage x Primary current = Secondary voltage x Secondary current.

GPE = mgh. Gravitational Potential Energy = mass x gravity x height.

KE = ½mv2. Kinetic Energy = 05 x mass x velocity2.

W = F x d. Work done = Force x distance.

W = E. Work done = Energy transferred.

s = d ÷ t. speed = distance ÷ time.

a = (v-u) ÷ t. acceleration = change in velocity ÷ time.

F = m x a. Force = mass x acceleration.

w = m x g. weight = mass x gravity.

p = m x v. momentum = mass x velocity.

mv - mu = F x t. change in momentum = Force x time.

p = F ÷ a. pressure = Force ÷ area.

d = m ÷ v. density = mass ÷ volume.

v = f x λ. wave speed = frequency x wavelength.
people can find different strategies effective but TBH I never used acronyms and tried to remember what the equation meant and as far as possible how they fitted together.

e.g.

P=VI
Q=It
E=VQ

fit together and it's imo more obvious if you rewrite them
I=Q/t (current is charge per unit time... or amps = Coulombs per second)
V=E/Q (PD is energy per unit charge... or volts = Joules per Coulomb)

and since power is energy per unit time or Watts per second...
you can see that if you've got 1 Joule per Coulombs flowing at a rate of 1 coulomb per second you can can multiply IV, cancel the Coulombs out and you're left with Joules per second.

GPE=mgh
comes from the more general eqn W=fd

mg is the weight (force acting vertically) and h is a vertical displacement

some of those eqns can be remembered visually as triangles...

e.g.

where the horizontal bar represent the bar in a fraction (i.e. division).
you use it by putting your thumb over the thing you're trying to find
V=IR... I multiplied by R
R=V/I

some of those things are quite everyday
speed on the roads is measured in miles per hour (or km per hour)
and either way it's unit of distance divided by a unit of time... an hour is measuring the same thing as a second (time) and a mile is measuring the same thing as a meter (distance) so meters per second is also a unit of speed... as would be yards per year etc.

similar thing for the pressure in your car or bike tyres - pressure is force per area so Newtons per m2 or pounds per sq inch (though confusingly pounds is a unit of force AND a unit of mass - so it's not used in science much)

VpIp=VsIs
is telling you that in an ideal transformer power in = power out
the ratio of turns np/ns equals the ratio Vs/Vp
so you couldn't put 110V at 5 amps into a transformer with a 1/2 turns ratio and get 220V at 5 amps out because that would mean creating power from nothing.
maximum current in that case would be 1/2 the primary current.

hope some of that helped.
1
#3
(Original post by Joinedup)
people can find different strategies effective but TBH I never used acronyms and tried to remember what the equation meant and as far as possible how they fitted together.

e.g.

P=VI
Q=It
E=VQ

fit together and it's imo more obvious if you rewrite them
I=Q/t (current is charge per unit time... or amps = Coulombs per second)
V=E/Q (PD is energy per unit charge... or volts = Joules per Coulomb)

and since power is energy per unit time or Watts per second...
you can see that if you've got 1 Joule per Coulombs flowing at a rate of 1 coulomb per second you can can multiply IV, cancel the Coulombs out and you're left with Joules per second.

GPE=mgh
comes from the more general eqn W=fd

mg is the weight (force acting vertically) and h is a vertical displacement

some of those eqns can be remembered visually as triangles...

e.g.

where the horizontal bar represent the bar in a fraction (i.e. division).
you use it by putting your thumb over the thing you're trying to find
V=IR... I multiplied by R
R=V/I

some of those things are quite everyday
speed on the roads is measured in miles per hour (or km per hour)
and either way it's unit of distance divided by a unit of time... an hour is measuring the same thing as a second (time) and a mile is measuring the same thing as a meter (distance) so meters per second is also a unit of speed... as would be yards per year etc.

similar thing for the pressure in your car or bike tyres - pressure is force per area so Newtons per m2 or pounds per sq inch (though confusingly pounds is a unit of force AND a unit of mass - so it's not used in science much)

VpIp=VsIs
is telling you that in an ideal transformer power in = power out
the ratio of turns np/ns equals the ratio Vs/Vp
so you couldn't put 110V at 5 amps into a transformer with a 1/2 turns ratio and get 220V at 5 amps out because that would mean creating power from nothing.
maximum current in that case would be 1/2 the primary current.

hope some of that helped.
Thank you!
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