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 (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
N
FN; Normal;Normal force ✔
f
Ff / fk / frictional force ✔
w
Fg; mg; Weight;FEarth on block;Fw ;Gravitational force ✔
T
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
OR
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
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
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
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 + ΔEk ✔ 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 ✔ ✔
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 (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.
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
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 mvi2
-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 - mghi = ½ m (vf2- vi2) + mg(hf - hi) Wnc = ½ mvf2 + mghf - ½ mvi2- mghi Wf + WF = ½ mvf2- ½ mvi2 + mghf - mghi 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
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)
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
OPTION 2
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
(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 J 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 m λo (threshold wavelength) < λ (incident wavelength) ∴ the ammeter will not register a current
11.4 (5)
OPTION 1
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
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.
Last modified on Wednesday, 22 September 2021 07:32