Formulas

Question 1

In the oscillation of a bob, the formula for a Period =

Answer 1

Time taken
_______________________
Number of oscillations

Question 2

When calculating the resultant force using arrows, the formula is what?

Answer 2

c^2 = a^2 + b^2

Question 3

Where u or v = speed

u or v =

Answer 3

S/t

Speed = distance travelled/time taken

Question 4

Average speed =

Answer 4

Total distance travelled
_________________________
Total time taken

Question 5

Where acceleration = a

a =

Answer 5

v - u
_____
t

Question 6

In a Distance - Time graph,
Speed =

Answer 6

The gradient i.e h/b

Question 7

In a diagram,
Gradient =

Answer 7

h/b

Question 8

In a speed - time graph,
Acceleration =

Answer 8

The gradient i.e h/b

Question 9

In a speed - time graph,

Distance travelled =

Answer 9

The size of the area under the graph

Question 10

When W = weight

W =

Answer 10

Mass x gravitational field strength
i.e
m x g

(mg)

Question 11

Where density = ρ
ρ =

Answer 11

ρ = mass/volume
(m/V)

Question 12

Where g = gravitational field strength

g =

Answer 12

W/m

Question 13

With F = size of the resultant force
the relationship between F, m and a is:

F =

Answer 13

Mass x acceleration

(F = m x a)
(F = ma)

• This applies t a case in which I each of the physical quantities in the equation are expressed in their SI Units.

Question 14

With x = extension

X =

Answer 14

Extended length - Original length
(X = L1 - L0)

Question 15

What is Gravity or the acceleration due to gravity =

Answer 15

9.8m/s^2
9.8N/kg

Question 16

Where k = spring constant
k =

Answer 16

Force
__________
Extension

the force is Weight
x = extension
(k = W/x)

Question 17

On an extension - force graph,
How how do you find the spring constant, k

k = gradient

Gradient =

Answer 17

h/b

Question 18

Where a moment is the turning effect of a force,

Moment =

Answer 18

Force x perpendicular distance of the force from the pivot
(Moment = F x |_ d)
(M = Fd)

Question 19

What is the formula for momentum where p = momentum?

Answer 19

Momentum = mass x velocity
{p = mv}

The units for this can either be Ns or kgm/s

Question 20

Impulse is change in momentum.

What is the formula for impulse?

Answer 20

Impulse = Change in momentum
i.e Final Momentum – Initial momentum

{Impulse = m{v–u}

Question 21

If in the case of Impulse, m{v–u} = Impulse
and and v-u/t = acceleration, then Impulse = mat
And if ma = F

Then Impulse can also be equal to what?

Answer 21

Impulse = Ft

Where:
F is Force
t is time
m is mass
a is acceleration
v or u is velocity

Question 22

What is the relationship between Impulse and Force?

Answer 22

Force = Impulse/time taken

F=impulse/t

Question 23

In the case of a collision, the relationship between the momentum of two different bodies is what?

Answer 23

The relationship between the momentum of two bodies in collision is:

m1 x v1 = m2 x v2

{mass 1 x velocity 1 = mass 2 x velocity 2}
{Initial momentum = Final Momentum}

This is due to conservation of momentum.

Question 24

In the case of a collision, in which one body causes the movement of another, what is the formula, based on momentum, to find the final velocity?

Answer 24

Final velocity after the collision of two moving bodies is found using the formula:

{m1 x v1} + {m1 x v2} = {m1 + m2}vf

{mass1 x velocity1} + {mass2 x velocity2} =
{mass1 + mass2} x final velocity

Question 25

What is the formula for the calculation of Kinetic energy?

Answer 25

Ek = 1/2m.v^2

This is where v = speed because Kinetic energy is a scalar quantity, like all forms of energy.

Question 26

The formula for the calculation of Gravitational potential energy is what?

Answer 26

Ep = mgh

m = mass
g = gravitational field strength
h = height

Question 27

The formula for the calculation of change in Gravitational potential energy is what?

Answer 27

ΔE = mgΔh

m = mass
g = gravitational field strength
Δh = change in height

ΔEp can also be found using the formula:
ΔEp = Ep(f) - Ep(i)

Question 28

The formula to calculate Work done is what?

Answer 28

Work done = Force x Distance moved in the direction of the force

Work Done = F x d

Question 29

The relationship between Work done (Fd) and Ep (mgh), is what?

Answer 29

With mass x gravitational field strength = Weight
the formula for Ep can be written as:
Ep = Weight x height
And since weight is a gravitational force,

Ep = Work done

because potential energy equals the work done in moving to that point.

Because Work done = Energy transformed

Ek = Work done

Question 30

What is the formula to find power, which is measured in Watts, with
1 J/s = 1 Watt?

Answer 30

Power = Work done ÷ time
(P = Work done/t)

This can also be broken down to
Power = Change in Energy ÷ time
Power = ΔE/t

Question 31

With Power = Work done/time,
Work done = ?

Answer 31

Work done = Power x time

Question 32

What is the formula for the calculation of Energy input?

Answer 32

Energy Input = Useful energy + Wasted energy

Question 33

What is the formula for the calculation of Efficiency?

Answer 33

Efficiency =
Useful Energy Output ÷ Total energy output x 100%
or
Useful Power Output ÷
Total Power Output x 100%

Question 34

What is the formula for the calculation of pressure?

Answer 34

Pressure = Perpendicular Force ÷ Area
(P = F/A)

The units for Pressure are N/m^2 or Pascals(Pa), with 1 N/m^2 = 1 Pa

Question 35

In solids particularly, the formula for pressure is what?

Answer 35

Pressure = Weight ÷ Area of contact
(P = W/A)

Question 36

In liquids particularly, the formula for pressure is what?

Answer 36

Pressure = Density x height x gravitational field strength

P = ρhg
ρ = density

Question 37

What is the formula for the representation of the fact that, for a fixed mass of gas, kept at a constant temperature, the pressure is inversely proportional to the volume?

Answer 37

This is represented by the formula:

P1 V1 = P2 V2
or
P ∝ I/V
or
PV = constant

Question 38

If P1 V1 = P2 V2 then

P1 = ?

Answer 38

P1 = (P2 V2)/V1

This applies to any of the components of the equation.

Question 39

Where c = specific heat capacity

c = ?

Answer 39

c =
Δ E
_________
mΔθ

ΔE = change in energy (may be substituted for Q)
m = mass
Δθ = change in temperature

The unit commonly used for this is J/Kg/ºC

Question 40

Energy supplied can be calculated from Power and time taken, what is the formula for thus?

Answer 40

∆E = P x t

Change in Energy = Power x time taken

Question 41

With f = frequency
Frequency is the number of complete cycles of a wave per unit time.
f = ?

Answer 41

f = N/t

Number of complete cycles
____________________________
time

N = number of complete cycles
t = time

Question 42

In reference to waves T = Period
The Period of a wave is the duration of a complete cycle.
What is the relationship between f and T?
f = ?

Answer 42

f = 1/T
or
T = 1/f

This is because
f = N/t
t/T = N
t = NT

t = time
T = Period
N = number of complete cycles

Question 43

How do you calculate Wave Speed, V, with distance and time, where:
- distance travelled = wavelength = λ
- time taken to travel one wavelength = Period = T

Answer 43

Wave Speed =
distance travelled
___________________
time taken

wavelength
____________
Period

v = λ/T
v = λ x 1/T
since f = 1/T
v = f x λ

Wave Speed = frequency x wavelength