PHYSICAL SCIENCES
PAPER 1
GRADE 12
NSC EXAMS
PAST PAPERS AND MEMOS NOVEMBER 2018

MEMORANDUM

QUESTION 1
1.1 C /D✔✔ (2)
1.2 C ✔✔ (2)
1.3 C ✔✔ (2)
1.4 B ✔✔ (2)
1.5 B ✔✔ (2)
1.6 A ✔✔ (2)
1.7 A ✔✔(2)
1.8 D ✔✔ (2)
1.9 D ✔✔ (2) 
1.10 C ✔✔ (2) [20]

QUESTION 2
2.1  (2) 

When a (non-zero) resultant/net force acts on an object, the object will  accelerate in the direction of the force with an acceleration that is directly  proportional to the force and inversely proportional to the mass of the object.  ✔✔
OR
The (non-zero) resultant/net force acting on an object is equal to the rate of  change of momentum of the object in the direction of the resultant/net force.  ✔✔ (2 or 0) 
ACCEPT
Acceleration is directly proportional to the net force and inversely proportional  to the mass of the object. 

NOTE

  • If any of the underlined key words in the correct context is omitted deduct 1  mark. 

2.2 
1 JYGUAGUD(4) 

Notes

  • Mark is awarded for label and arrow
  • Do not penalise for length of arrows 
  • If T is not shown but T|| and T⊥ are shown, give 1 mark for both
  • If force(s) do not make contact with body : Max/Maks: 3/4
  • Deduct 1 mark for any additional force  
 

Accept the following symbols 

FN; Normal;Normal force ✔

f

Ff / fk / frictional force ✔

w

Fg; mg; Weight;FEarth on block;Fw  ;Gravitational force ✔

Tension ; FT /FA, F /16,96 N ✔

2.3.1  (1) 

The 2/8 kg block /system is accelerating ✔
OR
The acceleration is not zero / a ≠ 0 (m·s-2) / a = 1,32 m.s-2✔
OR
Velocity is /increasing/changing/not constant ✔
OR
Fnet is not equal to zero  ✔
OR
The acceleration is changing  ✔
Accept

  • An unbalanced force is acting on it  ✔ 

2.3.2 (3) 

For 2 kg 
Fnet = ma  {1 mark for any }    Fnet = ma  
mg -T= ma                              mg + T = ma  ✔ 
(2)(-9,8) + T = 2(-1,32) ✔   (2)(9,8) – T = 2(1,32) ✔ 
T = 16,96 N ✔                       T = 16,96 N ✔ 

2.3.3  (4) 

POSITIVE MARKING FROM 2.3.2
2 JYGUYAgduj
OR
3 HFGATYD

2.4  (1) 

  • ANY ONE
    Normal force changes/decreases ✔
  • The angle (between string and horizontal) changes/increases. 
  • The vertical component of the tension changes/increases 

2.5  (2)   [17] 

Yes✔
The frictional force (coefficient of friction) depends on the nature of the surfaces  in contact. ✔ 
ACCEPT
The nature of the surface changes / µk changes  

QUESTION 3
3.1 (2) 

Downwards ✔ 
The only force acting on the object is the gravitational force/weight which acts  downwards.✔
ACCEPT

  • The only force acting is gravitational/weight.✔
    OR
  • Gravitational force/weight acts downwards.✔
    OR
  • The ball is in free-fall ✔✔
    OR
  • (Gravitational) acceleration is downwards✔✔

OPTION 1
Upward positive
vf = vi + aΔt ✔ 
0 = 7,5 + (-9,8)Δt ✔ 
Δt = 0,77 s ✔ 

Downward positive
vf = vi + aΔt ✔ 
0 = -7,5 + (9,8)Δt ✔
Δt = 0,77 s ✔

3.2  (3)

OPTION 2
Upward positive 
At highest point vf is zero 
vf2 = vi2 + 2aΔy
0 = (7,5)2 + (2)(-9,8)Δy
Δy = 2,87 (2,869)m
4 jhgayaduguy
Δt = 0,77 s✔ 

OPTION 2
Downward positive 
At highest point vf is zero 
vf2 = vi2 + 2aΔy
0 = (-7,5)2 + (2)(9,8)Δy
Δy = 2,87 (-2,869)m
5 jyguatygduja
Δt = 0,77 s✔ 

OPTION 3
Upward positive 
FnetΔt = m(vf – vi) ✔
mgΔt = m(vf – vi) 
(-9,8)Δt = 0 – 7,5 ✔
∴ Δt = 0,76531 s (0,77 s) 

OPTION 3
Downward positive 
FnetΔt = m(vf – vi) ✔
mgΔt = m(vf – vi) 
(9,8)Δt = 0 –(- 7,5) ✔
∴ Δt = 0,76531 s (0,77 s)✔

OPTION 4
Upward positive 
(Top to Bottom ) 
vf = vi + aΔt ✔
-7,5 = 0 + (-9,8)Δt ✔
∴ Δt = 0,76531 s (0,77 s) ✔

OPTION 4
Downward positive 
(Top to Bottom ) 
vf = vi + Δt ✔
7,5 = 0 + (9,8)Δt✔
∴ Δt = 0,76531 s (0,77 s) ✔

OPTION 5
Upward positive 
(Top to Bottom) 
vf2 = vi2 + 2aΔy 
(7,5)2 = (0)2 + 2(-9,8)Δy 
Δy = -2,87 m 
Δy = viΔt + ½ aΔt2
-2,87 = (0)Δt + ½ (-9,8)(Δt)2 
Δt = 0,765 s ✔

OPTION 5
Downward positive 
(Top to Bottom ) 
vf2 = vi2 + 2aΔy 
(7,5)2 = (0)2 + 2(9,8)Δy 
Δy = 2,87 m Δy = viΔt + ½ aΔt2 ✔
2,87 = (0)Δt + ½ (9,8)Δt2
Δt = 0,765 s ✔

NOTES for marking QUESTION 3.3 

 

Formula mark

Substitution mark

✔✔

Mark for height/distance  

Mark for comparison

Mark for conclusion

3.3  (6) 

OPTION 1
Upward positive
At highest point vf is zero
vf2 = vi2 + 2aΔy
0✔ = (7,5)2 + (2)(-9,8)Δy ✔ 
Δy = 2,87 (2,869) m✔ 
This is higher than height needed to reach point T (2,1 m)✔therefore the ball will pass point T.✔ 

Downward positive
At highest point vf is zero
vf2 = vi2 + 2aΔy
0✔ = (-7,5)2 + (2)(9,8)Δy✔ 
Δy = - 2,87 (-2,869) m✔ 
This is higher than height needed to reach point T (2,1 m)✔therefore the ball will pass the target. ✔ 

OPTION 2
(POSITIVE MARKING FROM 3.2) 
Upward positive
Δy = viΔt + ½ aΔt2✔ 
Δy = (7,5)(0,77) ✔ + ½ (-9,8)(0,77)2✔  
Δy = 2,87 m (2,86 m)✔ 
This is higher than height needed to reach point T (2,1 m)✔therefore the ball will pass point T. ✔ 
Downward positive
Δy = viΔt + ½ aΔt2✔ 
Δy = (-7,5)(0,77) ✔ + ½ (9,8)(0,77)2✔  
Δy = -2,87 m (2,869 m)✔ 
This is higher than the height needed to reach point T (2,1 m)✔therefore the  ball will pass point T.

OPTION 3
(Emech)Top = (Emech)Ground
1 mark for any 
(EP +EK)Top = (EP +EK)Bottom
(mgh + ½ mv2)Top = (mgh + ½ mv2)Bottom 
(9,8)(h) + 0 ✔= 0 + (½ )(7,5)2 ✔ 
h = 2,87 m (2,869 m)✔ 
This is higher than height needed to pass the target (2,1 m)✔therefore the ball will pass the target.✔ 

OPTION 4
Wnet = ∆EK 
mgΔxcosθ = ½ mvf2- ½ mvi2 ✔ 
(9,8)Δxcos180º✔ = 0 - ½(7,5)2✔ 
Δx = 2,87 m (2,869 m)✔ 
This is higher than point height needed to pass point T (2,1 m)✔therefore the  ball will pass point T. ✔ 

OPTION 5
Upward positive
If the highest point is yf then Δy = (yf – y1,6) At highest point vf is zero
vf2 = vi2 + 2aΔy
0✔ = [(7,5)2 + (2)(-9,8)(yf – 1,6)]✔ 
yf = 4,47 (4,469) m✔ 

Yes ✔ ✔ 
OR
This point (4,47m) is higher than point T ✔ ✔  (or even the required height of  2,1 m) therefore the ball will pass point T. 

Downward positive
If the highest point is yf then Δy = (yf – y1,6)
At highest point vf is zero
vf2 = vi2 + 2aΔy
0✔ = [(-7,5)2 + (2)(9,8){yf – (-1,6)}] ✔ 
yf = -4,47 (-4,469) m✔ 
height is  is 4,47 m. 
This point (4,47 m) is higher than point T✔✔ (or even the required height of  2,1 m) therefore the ball will pass point T. 

OPTION 6 (POSITIVE MARKING FROM 3.2) 
Upward positive
If the highest point is yf then Δy = (yf – y1,6) At highest point vf is zero
Δy = viΔt + ½ aΔt2✔ 
(yf – 1,6) = (7,5)(0,77) ✔ + ½ (-9,8)(0,77)2✔  
yf = 4,47 m (4,469 m)✔ 
This point (4,47m) is higher than point T ✔✔ (or even the required height  of 2,1 m) therefore the ball will pass point T. 

Downward positive
If the highest point is yf then Δy = (yf – y1,6) At highest point vf is zero 
Δy = viΔt + ½ aΔt2✔ 
{yf – (-1,6)} = (-7,5)(0,765) ✔ + ½ (9,8)(0,765)2✔  
yf = -4,47 m (-4,469 m)✔ 
This point (4,47m) is higher than point T✔✔ (or even the required height of  (2,1m) therefore the ball will pass point T. 

OPTION 7 (POSITIVE  MARKING FROM 3.2) 
Upward positive
6 ujy gayd
This is higher than height needed to  pass the target (2,1 m)✔therefore the  ball will pass the target.✔ 

OPTION 7(POSITIVE  MARKING FROM 3.2 
Downward positive
7 jkguaygdgi
Height  is 2,89m 
This is higher than height needed to  pass the target (2,1 m)✔therefore the  ball will pass the target.✔ 

OPTION 8 
Upward positive
At highest point vf is zero
vf2 = vi2 + 2aΔy
0✔ = vi2 – (2)(9,8)(2,1) ✔ 
vi = 6,42 m∙s-1 ✔ 

  • This is the actual velocity needed to reach the target.
  • The given velocity is greater than the actual velocity needed. ✔
  • The ball will pass the target. ✔ 

Downward positive
At highest point vf is zero 
vf2 = vi2 + 2aΔy
0✔ = vi2 + (2)(9,8)(-2,1) ✔ 
vi = 6,42 m∙s-1 ✔ 

  • This is the actual velocity needed to pass the target.
  • The given velocity is greater than the actual velocity needed. ✔
  • The ball will reach the target. ✔ 

OPTION 9
Wnc = ΔEp + ΔE✔ 
0 = mghf – mghi + ½ mvf2 – ½ mvi2 
0 ✔ = (9,8)hf – (9,8)(1,6) + ½ (0) 2 – ½ (7,5)2✔ 
 0 = (9,8)hf – 43,805 
∴ hf = 4,47 m ✔ 
∴ The ball will pass point T ✔ ✔ 

OPTION 10
POSITIVE MARKING FROM 3.2
Upward positive
Δt(max. height/maks. hoogte) = 0,77 s 
Δy = viΔt + ½ aΔt2 ✔ 
2,1✔  = (7,5)Δt + ½ (-9,8)Δt2 ✔ 
∴ Δt = 0,36 s ✔ 
∴ Δt (max height, 0,77 s) > Δt (to pass point T 0,36 s) ✔ 
∴ The ball passed point T ✔ 

Downward positive
Δt (max height) = 0,77 s 
Δy = viΔt + ½ a Δt2 ✔ 

2,1✔ = (7,5)Δt + ½ (-9,8)Δt2 ✔ 
∴ Δt = 0,36 s✔ 
∴ Δt (max height, 0,77 s) > Δt (to reach point T, 0,36 s) ✔ 
∴ The ball passed point T ✔ 

OPTION 11
Upward positive
∆y = vi∆t + ½ a∆t2✔ 
(3,7 – 1,6)✔  = 7,5 ∆t + ½ (- 9,8) ∆t2 ✔ 
∆t = 0,375 s ✔ 
The time to pass point T is less than time to reach maximum height ✔ . Ball  will pass point T.✔ 

Downward positive
∆y = vi∆t + ½ a∆t2✔ 
(3,7 – 1,6)✔  = -7,5 ∆t + ½ (9,8) ∆t2 ✔ 
∆t = 0,375 s ✔ 
The time to reach point T is less than time to reach maximum height ✔ . Ball  will pass point T.✔ 

OPTION 12
Upward positive
vf2 = vi2 + 2aΔy ✔ 
vf2 = (7,5)2 ✔ + 2(-9,8)(2,1) ✔ 
vf = 3,88 m·s-1 ✔ 
Velocity at T is 3,88 m·s-1therefore the ball still moving towards its maximum height ✔ ✔ 

Downward positive
vf2 = vi2 + 2aΔy ✔ 
vf2 = (-7,5)2 ✔ + 2(9,8)(-2,1) ✔ 
vf = -3,88 m·s-1 ✔ 

Velocity at T is -3,88 m·s-1therefore the ball is still moving towards its  maximum height ✔✔

3.4 POSITIVE MARKING FROM 3.2 
8 kuhkahgduyha (2) [13] 

Notes

 

Initial velocity and time for final velocity shown  

Correct straight line (including orientation) drawn  

   

QUESTION 4
4.1 Momentum is the product of the mass of an object and its velocity ✔✔
[NOTE: 2 or/of 0] (2)
4.2 To the left ✔
Newton's third law✔
ACCEPT:

  • Principle of conservation of linear momentum / law of action-reaction✔
  • Newton's third law and Newton’s second law ✔ (2) 

NOTE: For QUESTION 4.3 and 4.4 motion to the right has been taken as positive. Candidates may use the opposite direction. 
9 gujyagdyug
4.5  (2)  [14]

POSITIVE MARKING FROM 4.4 /POSITIEWE NASIEN VANAF 4.4 32 kg⋅m⋅s-1/ N·s  to the right/opposite direction /na regs /teenoorgestelde  rigting 

QUESTION 5 
5.1

  • A force is non-conservative if the work it does on an object which is moving  between two points depends on the path taken✔✔
    OR
  • A force is non-conservative if the work it does on an object depends on the  path taken.✔✔
    OR
  • A force is non-conservative if the work it does in moving an object around a  closed path is non-zero ✔✔. (2) 

NOTE

  • If any of the underlined key words/phrases in the correct context is omitted  deduct 1 mark. If the word work is omitted 0 marks  .

5.2 No ✔ (1) 
5.3 (3)

OPTION 1
P =  W✔ 
       Δt
= 4,8×106✔ 
      (90) 
 = 53 333,33 W  
 = 5,33 x 104 W (53,33 kW) ✔ 

OPTION 2
10 ikjgajyd
 WF = FΔxcosθ 
4,80 x 106 = F(1 125)cos0º
 F = 4 266,667 N 
Pave = Fvave 
 = (4 266,667)(12,5) 
 = 53 333, 33 W 

5.4

  • The net/total work done on an object is equal to the change in the object's  kinetic energy✔✔
    OR
    The work done on an object by a net force ✔is equal to the change in the  object's kinetic energy. ✔  (2) 

NOTE

If any of the underlined key words/phrases in the correct context is omitted  deduct 1 mark. .

5.5 (5) (5) 

OPTION 1
Wnet = ΔK✔ 
Ww + Wf + WF = ½ mvf2- ½ mvi2 
mgΔxcosθ + Wf + WF = ½ mvf2- ½ mvi2 
(1 500)(9,8)200cos180º✔ + Wf + 4,8 x 106 ✔= ½ (1 500)(252 – 0) ✔
-2 940 000 + Wf +4,8 x 106 = 468 750 
Wf = -1 391 250 J 
 = -1,39 x 106 J✔ 

OR

Wnet = ΔK✔ 
Ww + Wf + WF = ½ mvf2- ½ mvi

-ΔEp + Wf + WF = ½ mvf2- ½ mvi2 
-(1 500)(9,8)(200 – 0)✔ + Wf + 4,8 x 106 ✔= ½ (1 500)(252 – 0) ✔
-2 940 000 + Wf +4,8 x 106 = 468 750 
Wf = -1 391 250 J 
 = -1,39 x 106 J ✔ 

NOTE

  • 0 can be omitted in above substitutions. 

OPTION 2
1 mark for any of  these
Wnc = ΔK + ΔU 
Wnc = ½ mvf2- ½ mvi2 + mghf - mgh
 = ½ m (vf2- vi2) + mg(hf - hi) 
Wnc = ½ mvf2 + mghf - ½ mvi2- mgh
 Wf + WF = ½ mvf2- ½ mvi2 + mghf - mgh
Wf + 4,8 x 106 ✔= [½ (1 500)(25)2 + -0] ✔+[(1 500)(9,8)(200) - 0]✔ 
Wf = - 1,39 x 106 J (-1,40 x 106J )✔ 

OR

1 mark for any of  these
Wnc = ΔK + ΔU 
Wnc = ½ mvf2- ½ mvi2 + mghf - mghi 
 = ½ m (vf2- vi2) + mg(hf - hi) 
Wnc = ½ mvf2 + mghf - ½ mvi2- mghi 
Wf + 4,8 x 106 ✔= [½ (1500)(25)2 + (1500)(9,8)(200)] - [0 + 0] 
Wf = - 4,8 x 106 + 3,4 x 106 
 = - 1,39 x 106 J (-1,40 x 106J )✔ 

ACCEPT THE FOLLOWING FOR: 3 /5
POSITIVE MARKING FROM 5.3
vf = vi + aΔt 
25 = 0 + a(90) 
a = 0,277…m\s-2 
Fnet = ma  
 =(1 500)(0,2777…) = 416,66… N 
F + (w||) + (-fk) = 416,666… 
4 266,6667 – 1 500(9,8)sinθ - fk = 416,666… 
fk = 1 236,6667 N 
Wf = fkΔxcosθ 
 = (1 236,6667)(1 125)(cos180°)
 = - 1 391 250 J 

(5) [13]

Related Items

QUESTION 6
6.1

  • The change in frequency (or pitch), of the sound detected by a listener because the sound source and the listener have different velocities relative to the medium of sound propagation.
    OR
  • An (apparent) change in observed/detected frequency (pitch), as a result of the  relative motion between a source and an observer  (listener).  (2) 

NOTE

If any of the underlined key words/phrases in the correct context is omitted  deduct 1 mark. 

6.2 Away from✔ 
Observed frequency lower  (2) 
6.3 (3) 

v = fλ ✔ 
340 = f (0,34) ✔ 
 f = 1 000 Hz ✔ 

6.4 

POSITIVE MARKING FROM 6.3
11 jhgvagtdhd
Accept:
12 hafysdd

(6) [13] 

QUESTION 7
7.1  (2)   

Qnet  = Q1 + Q2 + Q3 
                     3 
-3 x 10-9 = 15 × 10-9 +  Q  + 2x10-9 
                                  3 
Q = + 4 x 10-9 C✔ 
NOTE

  • for addition of the three correct charges 
  • correct answer 

13 jgajydgud
NOTES

  • Correct shape ✔
  • Correct direction ✔
  • Lines must not cross and must touch spheres ✔ (3) 

7.3 The magnitude of the electrostatic force exerted by one point charge (Q1) on  another point charge (Q2) is directly proportional to the product of the  (magnitudes) of the charges and inversely proportional to the square of the  distance (r) between them ✔✔ (2)

NOTE

  • If any of the underlined key words/phrases in the correct context is omitted  deduct 1 mark. If masses used (0/2) 

7.4 (5) 
OPTION 1
14 jhgaydguagd
OPTION 2
15 ytfajydtafd
7.5  (3)

POSITIVE MARKING FROM 7.4 
OPTION 1
E = F
       q
= 8,15 × 10-6
    3 ×  10-9
 = 2,72 x 103 N.C-1 ✔ 

OPTION 2
ES = KQ
         r2
= (9×109)(3×10-9
         (0,1)2
 = 2 700 N.C-1 

ET = KQ
         r2
= (9×109)(3×10-9
         (0,3)2
 = 300 N.C-1 

Enet = √ (ES2 + ET2)
= √  (2700)2 +(30)2
 = 2 716,62 N.C-1  

NOTE
Mark Allocation

  • Correct formula
  • both subsitutions
  • correct answer

If calculation done in 7.4 award full marks for answer written here.

7.6.1 Sphere P or/of T✔ (1) 
7.6.2 
16 ujyaudyd(3)[19]

QUESTION 8 
8.1

  • The battery supplies 12 J per coulomb/12 J per unit charge. ✔ ✔OR
  • The potential difference of the battery in an open circuit is 12 V. ✔ ✔OR
  • The battery does 12 J of work per coulomb of charge.✔ ✔ OR
  • Maximum work done by the battery per unit charge is 12 J  ✔ ✔ OR
  • Maximum energy supplied by the battery per unit charge is 12 J  ✔ ✔ OR
  • The battery supplies 12 J of energy per coulomb/ 12 J of energy per unit  charge ✔ ✔ OR
  • The greatest potential difference that can be generated by a battery is 12V ✔ ✔ OR
  • The total energy transferred by a battery to a unit electric charge is 12 J  ✔ ✔ OR
  • The total amount of electric energy supplied by the battery per coulomb/per  unit charge is 12 J ✔ ✔  (2) 

NOTE
If any of the underlined key words/phrases in the correct context is omitted  deduct 1 mark. 

8.2.1  (3) 

OPTION 1
Vlost = I r 
 = (2) (0,5) 
 = 1 V 
Vext  = Emf – Vlost 
 = (12 - 1) 
 = 11 V

OPTION 2
ε = I(R + r) 
12 = Vext +(2)(0,5) 
Vext = 11 V

OPTION 3
ε = I(R + r)
12 = 2(R + 0,5)
R = 5,5 Ω 
V = IR  
 = 2(5,5)
 = 11 V 

8.2.2  (2)

POSITIVE MARKING FROM 8.2.1
OPTION 1
R =
       I
 =  11 
      2
 = 5,5 Ω

OPTION 2
0,5:R 
 1:11 
R = 5,5 Ω 

OPTION 3
 1  =  11 
0,5    R 
R = 5,5 Ω 

OPTION 4
Vtotal = IRtotal 
12 = (2)Rtotal 
Rtotal = 6 Ω
R = 6 – 0,5 
 = 5,5 Ω 

OPTION 5 
ε = I(R + r) 
12 = 2(R + 0,5) 
R = 5,5 Ω 

8.3 Decreases 

  • Total resistance decreases ✔
  • Current increases ✔
  • "Lost volts" increases, (emf the same) ✔
  • External potential difference decreases ✔
    OR
  • Decreases ✔
  • Total resistance decreases  ✔
  • Current increases ✔
  • ε = Vext + Ir ✔
  • Ir increases ✔
  • ε is constant ✔
    ∴Vext/eks decreases (4) [11] 

QUESTION 9
9.1 Temperature/Temperatuur ✔ (1)
9.2.1 r = 3 Ω or/of 1,5 Ω ✔✔

  • Accept for one mark only:
    r = -3 Ω ✔ or -1,5 Ω (2) 

9.2.2 (3) [6] 

ε = slope (gradient) of the graph✔

  • Accept any correct values from the graph 

ε = 7,5 -(-3)
       1,5 -0 
 = 7 V  ✔

OR

POSITIVE MARKING FROM 9.2.1 
R = ε- r 
       I

  • Accept any correct values on the line from the graph 

7,5 = 1,5ε -3
ε= 7 V  ✔

OR

ε = I(R + r) 
 = 0,5(11 + 3) 
ε= 7 V  ✔

QUESTION 10
10.1.1 Y to/na X ✔ (1) 
10.1.2

  • Faraday’s Law Electromagnetic Induction ✔
    OR
  • Electromagnetic induction/Faraday's Law (1) 

10.1.3 Mechanical (kinetic) energy ✔to electrical energy ✔(2)
10.2.1 340 V ✔(1) 
Accept  -340 V 
10.2.2  POSITIVE MARKING FROM 10.2.1
17 ujygajydgyad(3) 

10.2.3 POSITIVE MARKING FROM  10.2.2 (3) [11] 
OPTION 1                                                                         OPTION 2
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OPTION 3
Pave =  VrmsIrms 
1600 = (240,416) Irms 
Irms = 6,66 A 
R = Vrms
       Irms 
= 240,416 
       6,66 
 = 36,1 Ω (36,09 Ω )

(Do not penalise if rms is omitted V) in R = Vrms
                                                                     Irms  

OPTION 4
Pave  =  VmaxImax
                    2 
1600 = 340Imax 
              2 
Imax = 9,412 A 
R = Vrms
       Irms 

 340    
    9,412 
 = 36, 12 Ω 

(Do not penalise if rms is omitted V) in R = Vrms
                                                                     Irms 

QUESTION 11
11.1  (2) 

Work function of a metal is the minimum energy needed to eject an electron  from the metal surface ✔✔

NOTE
If any of the underlined key words/phrases in the correct context is omitted  deduct 1 mark. 

11.2 (2) 

Potassium / Kalium / K ✔
fo for potassium is greater than fo for caesium 
OR
Work function is directly proportional to threshold frequency ✔
ACCEPT
Wo = hfo

Wo α fo

11.3  (3) 

OPTION 1
c = fλ 
3 x 108 = f(5,5 x 10-7
f = 5,45 x 1014 Hz 
fuv < fo of K(potassium) 
∴Ammeter in circuit B will not show a reading 

OPTION 2
E = hc (6,63 × 10-34)(3 × 108
       λ                5,5 × 10-7

 = 3,6164 x 10-19 J 
Wo = hfo = (6,63 x 10-34)(5,55 x 1014) = 3,68 x 10-19
Wo > E or hfo > hf 
∴The ammeter will not register a current 
Mark allocation

  • both correct formulae: E = hc and Wo = hfo 
                                                λ
  • both substitutions:  (6,63 × 10-34)(3 × 108
                                              5,5 × 10-7
     (6,63 x 10-34)(5,55 x 1014)
  • correct conclusion

OPTION 3
c = foλo
3 x 108 = (5,55 x 1014)λ 
λo = 5,41 x 10-7
λo (threshold wavelength) < λ (incident wavelength) 
∴ the ammeter will not register a current  

11.4 (5) 

OPTION 1
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NOTE: If EK of the incorrect   photocell is calculated, candidate   forfeit the mark for the final  answer. 
(6,63 × 10-34 )(3 x 108= (6,63 x 10-34)(5,07 x 1014) + Ek(max) 
      5,5  ×107
 EK = 2,55 x 10-20 J  (Range: 2,52 x 10-20 – 2,6 x 10-20 J) 

OPTION 2
POSITIVE MARKING FROM 11.3
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NOTE: If EK of the incorrect  photocell is calculated, candidate  forfeit the mark for the final  answer. 
(6,63 x 10-34)(5,45 x 1014) = (6,63 x 10-34)(5,07 x 1014) + Ek(max) 
EK = 2,52 x 10-20 J  (Range: 2,52 x 10-20 – 2,6 x 10-20 J) 

11.5 Remains the same (1) [13] 

TOTAL: 150

ADDENDUM 
QUESTION 7.2 
Accept the following electric field diagram which would be formed if the effect of the third  charge is considered. 
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Last modified on Wednesday, 22 September 2021 07:32