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[Pages:29]Answers to CSEC? Physics Examination Practice

Section A

2 a One mark for each pair of correct values. [5]

Time for 1 oscillation (period), T (s) 1.42 1.54 1.68 1.80 1.90 2.01

Period squared, T2 (s2) 2.01 2.37 2.83 3.24 3.61 4.04

b Graph plotted for a maximum of [7] marks.

B ? Best-fit line (curved or straight) [1]

L ? Labelled axes [1]

A ? Axes correct (correct quantities on x-axis and y-axis) [1]

P ? Plotting points: 5?6 points correct [3]; 3?4 points correct [2]; 1?2 points correct [1]

S ? Suitable scale for each axis [1]

c Maximum [4] marks.

Large triangle drawn to identify co-ordinates. [1]

Gradient formula: S =

y2 ? x2 ?

y 1 x 1

[1]

Values

read

correctly,

for

example:

S

=

0.98 m 3.90 s2

? 0.58 m ? 2.30 s2

0.40 m = 1.60 s2 [1]

Correct answer with unit: S = 0.25ms?2 [1]

d

g

=

42

?

l T2

Identifying

that

l T2

is

the

slope:

g =

4(3.14)2

?

slope

[1]

Substituting correct values: g = 39.4 ? 0.25ms?2 [1]

g = 9.85ms?2 [1]

e When l = 0.35m, T2 = 1.4s2 [1]

Therefore, T = 1.4 s2 [1]

T = 1.18 s [1]

f i When the length is shortened the period is also shortened. [1]

ii The mass of the bob would not affect the period. [1]

The angle of the pendulum will not affect the period. [1]

CSEC? Physics Examination Practice ? Aldaine Minott 2016

1

ANSWERS TO CSEC? PHYSICS EXAMINATION PRACTICE

3 a One mark for each correct answer. [6]

Pull force, F (N) 10 15 20 25 30 35

Pull length, l (cm) 31.0 41.9 52.8 63.7 74.6 85.5

Extension, x (m) 0.218 0.327 0.436 0.545 0.654 0.763

b Graph plotted for a maximum of [7] marks.

B ? Best-fit line (curved or straight) [1]

L ? Labelled axes [1]

A ? Axes correct (correct quantities on x-axis and y-axis) [1]

P ? Plotting points: 5?6 points correct [3]; 3?4 points correct [2]; 1?2 points correct [1]

S ? Suitable scale for each axis [1]

c Large triangle drawn to identify co-ordinates. [1]

Gradient formula: S =

y2 ? y1 x2 ? x1

[1]

Values

read

correctly,

for

example:

S

=

0.70 m 32 N

? ?

0.30 m 13 N

0.40 m = 19 N [1]

Correct answer with unit: S = 0.021mN?1 [1]

d

k

=

1 S

k

=

1 0.021m N?1

[1]

k = 47.6Nm?1 [1]

e i When F = 18N, x = 0.39m [1]

Ep

=

1 2

kx

2

Ep

=

1 2

?

47.6

?

(0.39)2

[1]

Ep = 3.62J [1]

ii Some of the energy transferred is transferred to heat which warms up the rubber band. The transfer to thermal energy will lower the potential energy stored in the stretched rubber. [2]

f The spring constant would increase. [1]

4 a Graph plotted for a maximum of [7] marks.

B ? Best-fit line (curved or straight) [1]

L ? Labelled axes [1]

A ? Axes correct (correct quantities on x-axis and y-axis) [1]

P ? Plotting points: 5?6 points correct [3]; 3?4 points correct [2]; 1?2 points correct [1]

S ? Suitable scale for each axis [1]

2 CSEC? Physics Examination Practice ? Aldaine Minott 2016

b Large triangle drawn to identify co-ordinates. [1]

Gradient formula: S

=

y2 x2

? ?

y1 x 1

[1]

Values

read

correctly,

for

example:

S

=

124 ?C 350 s

? 36 ?C ? 40 s

=

88 ?C 310 s

[1]

Correct answer with unit: S = 0.28?Cs?1 or 0.28Ks?1 [1]

c After 60s, T = 42?C [1]

= 42 + 273

= 315K [1]

d c

=

P m

?

1 S

=

140 W 1.3 kg

?

1 0.28 K s?1

[2]

= 385Jkg?1K?1 [2]

e i Heat capacity is the thermal energy required to raise the temperature of a body by one degree Celsius [1] without a change of state. [1]

EH = cT [1] ii C = mc [1]

iii C = 1.3kg ? 385Jkg?1K?1 [1]

= 501JK?1 [1]

Therefore, the metal which is most likely to be the sample is copper. [1]

f Tick in DOWN box [1]

5 a Completed table [3] (1 mark for each two correct values)

Time (years) 0 1900 4200 7700 13500 19000 24000

Percentage (remaining %) 100 80 60 40 20 10 5

Mass remaining (g) 10.0 8.0 6.0 4.0 2.0 1.0 0.5

b Graph plotted for a maximum of [7] marks. B ? Best-fit line (curved or straight) [1] L ? Labelled axes [1] A ? Axes correct (correct quantities on x-axis and y-axis) [1] P ? Plotting points: 5?6 points correct [3]; 3?4 points correct [2]; 1?2 points correct [1] S ? Suitable scale for each axis [1]

c Half-life is the time taken [1] for half of the radioactive nuclei in a material to decay. [1]

CSEC? Physics Examination Practice ? Aldaine Minott 2016

Section A

3

ANSWERS TO CSEC? PHYSICS EXAMINATION PRACTICE

d 10.0

9.0

8.0

7.0

Mass remaining (g)

6.0

5.0

1st t?

4.0

3.0

2nd t?

2.0 3rd t?

1.0

0

0

2500

5000

7500 10 000 12 500 15 000 17 500 20 000 22 500 25 000

Time (years)

1st half-life is when remaining mass has decreased to 50% [1]

t1 = 5700 years [1]

2

2nd half-life, t1 = 11250 years ? 1st t1 [1]

2

2

= 11250 years ? 5700 years [1]

= 5550 years [1]

3rd half-life, t1 = 16650 years ? (1st t1 + 2nd t1) [1]

2

2

2

= 16650 years ? (5700 years + 5550 years) [1]

= 5400 years [1]

Average half-life = (5700 years + 5550 years + 5400 years) [1]

3

16650 years

=

3

= 5550 years [1]

e 1.6 g [2]

f beta decay [1]

6 a Graph plotted for a maximum of [7] marks.

B ? Best-fit line (curved or straight) [1]

L ? Labelled axes [1]

A ? Axes correct (correct quantities on x-axis and y-axis) [1]

4 CSEC? Physics Examination Practice ? Aldaine Minott 2016

P ? Plotting points: 5?6 points correct [3]; 3?4 points correct [2]; 1?2 points correct [1]

S ? Suitable scale for each axis [1]

b i Liquid [1]

ii Liquid and solid [1]

iii Solid [1]

c Dashed line drawn as shown at 53.2?C; [1] for drawing a horizontal line; [1] for correct temperature.

65 A

60

55

B

50

C D

45

Temperature, p (?C)

40

35

30 25 20 15 10

5

0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Time, t (s)

d i The thermal energy required to raise the temperature of a substance of mass 1kg by 1?C. [2]

ii The thermal energy needed to convert 1kg of a substance from solid to liquid without a change in temperature. [2]

e i EH = m ? c ? T [1] = 0.04kg ? 2140JK?1kg?1 ? (53.2?C ? 60?C) [2]

= ?582J (minus sign shows that energy is lost) [1]

ii EH = 8000J + 582J [1] = 8582J [1]

f Heat the paraffin wax until it has just melted and no more. [1]

The paraffin wax will begin solidifying almost straightaway [1], so she would need to work quickly to make the best use of the wax. [1]

CSEC? Physics Examination Practice ? Aldaine Minott 2016

Section A

5

ANSWERS TO CSEC? PHYSICS EXAMINATION PRACTICE

7 a Completed table; [2] (one mark for each correct pair)

Angle of incidence, i (?) Angle of refraction, r (?) Sin i Sin r

20 15 0.34 0.26

30 22 0.50 0.37

40 28 0.64 0.47

50 35 0.77 0.57

60 39 0.87 0.63

b i The incident ray, the refracted ray, and the normal to the surface of the interface between the two media all lie in the same plane. [2]

ii The sine of the angle of incidence divided by the sine of the angle of refraction is a constant. [2]

c Graph plotted for a maximum of [7] marks.

B ? Best-fit line (curved or straight) [1]

L ? Labelled axes [1]

A ? Axes correct (correct quantities on x-axis and y-axis) [1]

P ? Plotting points: 5?6 points correct [3]; 3?4 points correct [2]; 1?2 points correct [1]

S ? Suitable scale for each axis [1]

d Large triangle drawn to identify co-ordinates. [1]

Gradient formula: S =

y2 x2

? ?

y1 x1

[1]

Values

read

correctly:

S

=

0.81 0.60

? ?

0.27 0.20

=

0.54 0.40

[1]

Correct answer with unit: S = 1.35 [1]

e Refractive index of water [1]

f emergent angle = angle of incidence

i = 60? [1]

sin i sin r

= n [1]

sin60? sin r

= 1.35 from part d) [1]

sin

r

=

sin 60? 1.35

[1]

r = sin?1 (0.64)

= 40? [1]

g The greater the density of the material, the greater its refractive index. [1]

Therefore, the more the refraction of light through the material. [1]

8 a When a body is placed in a fluid, the weight of the fluid displaced is equal to the force upwards (upthrust) on the body. [2]

b Completed table [5] (one mark for each correct pair)

6 CSEC? Physics Examination Practice ? Aldaine Minott 2016

Weight of solid (N)

0.5 1.0 1.5 2.0 2.5 3.0

Weight of water displaced (N) 0.05 0.12 0.18 0.23 0.30 0.35

Upthrust (N)

0.05 0.12 0.18 0.23 0.30 0.35

Weight solid appears to have in water (apparent weight) (N) 0.45 0.88 1.32 1.77 2.20 2.65

c Graph plotted for a maximum of [7] marks.

B ? Best-fit line (curved or straight) [1]

L ? Labelled axes [1]

A ? Axes correct (correct quantities on x-axis and y-axis) [1]

P ? Plotting points: 5?6 points correct [3]; 3?4 points correct [2]; 1?2 points correct [1]

S ? Suitable scale for each axis [1]

d Large triangle drawn to identify co-ordinates. [1]

Gradient formula: S =

y2 x2

? ?

y1 x1

[1]

Values

read

correctly;

for

example:

S

=

0.33 N ? 2.8 N ?

0.08 N 0.7 N

=

0.25 N 2.1 N

[1]

Correct answer with unit: S = 0.119 [1]

e %Wloss = slope ? 100%

= 0.119 ? 100% [1]

= 11.9% [1]

f The percentage weight loss is greater in salt water than fresh water. [1]

The object would appear to weigh less in salt water than fresh water. [1]

This is because the upthrust on the body in salt water is greater than the upthrust on the body in fresh water. [2]

g The density. [1]

9 a Graph plotted for a maximum of [7] marks.

B ? Best-fit line (curved or straight) [1]

L ? Labelled axes [1]

A ? Axes correct (correct quantities on x-axis and y-axis) [1]

P ? Plotting points: 5?6 points correct [3]; 3?4 points correct [2]; 1?2 points correct [1]

S ? Suitable scale for each axis [1]

b Large triangle drawn to identify co-ordinates. [1]

Gradient formula: S =

y2 ? x2 ?

y1 x 1

[1]

CSEC? Physics Examination Practice ? Aldaine Minott 2016

Section A

7

ANSWERS TO CSEC? PHYSICS EXAMINATION PRACTICE

Values

read

correctly;

for

example:

S

=

1750 mA 87.5 mA

? 500 mA ? 25 mA

1250 mA = 62.5 mA [1]

Correct answer with unit: S = 20 [1]

c The ratio of secondary current to the primary current in the transformer. [1]

d Step-down transformer [1]

e

Np N S

=

IS Ip

[1]

From

the

graph,

IS Ip

is

equal

to

the

gradient

=

20

[1]

200 N s

=

20

200 20

=

Ns

10 = Ns [1]

f P = IV [1]

I =

P V

I =

24 12

W V

[1]

I = 2A [1]

g The keyboard is rated at 12V/30W, so the maximum current

the keyboard requires to function is given by

I

=

P V

=

30 W 12 V

= 2.5A. [2]

The adaptor only supplies a maximum of 2A, therefore

the keyboard power cuts out over 80% maximum volume

because above that point the keyboard demands more

current than the adapter can supply. [1]

Therefore the adaptor is the problem. [1]

h i a.c. voltages can be transformed to higher or lower voltages. [1]

ii Transferring electrical energy at a higher voltage reduces the power losses in the transmission lines. [1]

10 a Completed table [3] (one mark for each correct pair)

Object distance, u (cm) Image distance, v (cm)

1 u

(cm?1)

12.0

44.0

0.083

15.0

28.0

0.067

17.0

24.0

0.059

20.0

19.3

0.050

25.0

16.3

0.040

30.0

15.0

0.033

1 v

(cm?1)

0.023

0.036

0.042

0.052

0.061

0.067

8 CSEC? Physics Examination Practice ? Aldaine Minott 2016

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