Equations

Question 1

Hooke’s law equation

Answer 1

F=kx
Force in N
K= spring constant
x= distance stretched in cm

Question 2

Percentage uncertainty (single measurements)

Answer 2

Absolute uncertainty / measured value x100

Question 3

Percentage uncertainty (multiple measurements)

Answer 3

Half the range/ mean value x100

Question 4

Current

Answer 4

Charge / time
Current in amps
Time in seconds
Charge in coulombs/ C

Question 5

Drift velocity

Answer 5

I= naVe
I= current in Amps
n= density of charge carriers in electrons/m3
a= cross section of wire in m2
V= drift velocity m/s
e= charge of the carrier/ electron in C

Question 6

Weight N

Answer 6

Mass (kg) x 9.81

Question 7

Stress

Answer 7

Force/area
ō(sigma)= F/A
In Nm-2

Question 8

Energy stored in a spring (series)

Answer 8

1/k (total)=1/k1+1/k2

Question 9

Energy stored in a spring (parallel)

Answer 9

k (total)= k1+k2

Question 10

Workdone (constant force)

Answer 10

force (N) x distance (m)

Question 11

Workdone 1 (not constant force)

Answer 11

0.5 x extension^2 (m) x constant (Nm)

in J

Question 12

Workdone 2 (not constant force)

Answer 12

0.5 x force (N) x constant (Nm)

in J

Question 13

Stress equation

Answer 13

Stress (pa/ nm-2) = tension (Pa)/ area (m2)

Question 14

Strain equation

Answer 14

Ratio extension to original length

Stress/e (no units)= extension/ original length

Question 15

Young’s modulus

Answer 15

Ratio of stress over strain
Measure of stiffness
More useful as it can be used in direct comparisons
Force x length/ area x extension

Question 16

Yield limit

Answer 16

Point at which the material stops behaving elastically

Question 17

Ohms law/ resistance equation

Answer 17

Resistance (Ohms)= Voltage (V)/ Current (A)

Question 18

Power equation

Answer 18

Power= current^2 x resistance

Question 19

Terminal Potential Difference

Answer 19

V= E -Ir

• V, terminal pd
• E, electromotive force transferred into the circuit
• I, current
• r, internal resistance (the resistance the electrons have when going through the cell), can be useful because it limits the amount of current in a short circuit

Question 20

Voltage

Answer 20

Energy / charge

Question 21

4 power equations

Answer 21

P=V x I
P=E / t
P=I^2 x R
P=V^2 / R

Question 22

Resistance

Answer 22

Voltage / Resistance