ESAT

Question 1

What is the equation for sum of an infinite series?

Answer 1

S∞ = a/(1-r)
a = first term
r = common ratio (divide a term by its previous term)

Question 1

What should you remember to do for fission reaction?

Answer 1

• Take into account the incoming neutron
• Draw a basic diagram of what’s going on, then fill in the blanks

Question 2

What affects the rate of thermal energy emission?

Answer 2

The material and current temperature (NOT temperature difference)

Question 3

Two particles push each other apart from being stationary. How is the kinetic energy divided between them?

Answer 3

By the ratio of their masses (the more massive object has less kinetic energy)

Question 4

What are convection currents the result of?

Answer 4

The density of part of a liquid increasing AND the volume of that part increasing.

Question 5

What is the formula for pressure at depth?

Answer 5

p=ρgh (+air pressure if below atmosphere)

Question 6

What is sin30, sin 45, sin60?

Answer 6

1/2, 1/√2, √3/2

Question 7

What is cos30, cos45, cos60?

Answer 7

√3/2, 1/√2, 1/2

Question 8

What is tan30, tan45, tan60?

Answer 8

1/√3, 1, √3

Question 9

If an object is on a 30º slope, how can you work out the vertical height and the parallel weight component?

Answer 9

• Vertical height is half distance up slope
• Weight component parallel to slope is half of weight component

Question 10

What’s the triangle inequality condition?

Answer 10

a + b > c (where c is the longest side)

Question 11

How do you work out the efficiency of a transformer given that the voltage is as expected?

Answer 11

new current / expected current

Question 12

What should you do when performing calculations with large numbers?

Answer 12

Keep the numbers as fractions/ break up into (prime) factors, so you can cancel out numbers when dividing.

Question 13

If the question looks long-winded, or if you are even slightly unsure on how to do it…

Answer 13

FLAG, GUESS, SKIP

Question 14

Especially for longer questions, you should…

Answer 14

Read the OBJECTIVE first.

Question 15

When solving quadratics with large numbers…

Answer 15

Consider using the quadratic formula and guessing a sensible square root, especially if answer options aren’t surds

Question 16

For more complex circuit questions…

Answer 16

Always draw a very quick sketch, with numbers

Question 17

If one lamp is used in two different circuits…

Answer 17

It does not have the same value for R in both circuits, unless the current is the same.

Question 18

Formula for sector area using radians:

Answer 18

A = (1/2)r²θ

Question 19

Formula for arc length using radians:

Answer 19

s = rθ

Question 20

Formula for segment area using radians:

Answer 20

A = (1/2)(r²)(θ-sinθ)

Question 21

When working with large numbers, what should you do?

Answer 21

Consider using standard form.

Question 22

What should you do on every question?

Answer 22

After you’ve read the objective, skim the answers for potential eliminations.

Question 23

What is the left hand rule?

Answer 23

Force: thumb
Field: index
Current: middle

Question 24

Which side of the cell symbol is positive, which way does current flow, and which way do electrons flow?

Answer 24

- Positive is larger - Electrons flow N to P - Current flows P to N

Question 25

When talking about force on a wire in a magnetic field, what should you look out for?

Answer 25

Look out for whether the wire has coils in; multiply the wire length by the number of coils.

Question 26

What is the equation for resistivity?

Answer 26

R = (ρl)/A

Question 27

What is the equation for Young’s Modulus?

Answer 27

E = σ/ε = Stress/strain =(Force/area)/(extension/length)

Question 28

How do you calculate strain energy?

Answer 28

Strain energy = (1/2)Fx

Question 29

What is the sum of an arithmetic series?

Answer 29

Sn = (n/2)(a1+an) Sn = (n/2)(2a+(n-1)d)

Question 30

What's the equation for specific heat capacity?

Answer 30

Q = mcΔT

Question 31

When calculating depth from pressure, what should you remember to do?

Answer 31

For the value of p, use water pressure minus air pressure.

Question 32

What is the equation for refraction?

Answer 32

n1sinΘ1 = n2 sinΘ2

Question 33

What is sin(90-x)?

Answer 33

cosx

Question 34

How you work out the amplitude of a sound wave from how far the speaker oscillates?

Answer 34

You can't!

Question 35

What is the equation for sum of a geometric series?

Answer 35

Sn = a(r^n -1)/(r-1)