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South Pacific Form Seven Certificate

PHYSICS

2017

INSTRUCTIONS Write your Student Personal Identification Number (SPIN) in the space provided on the top right hand corner of this page. Answer ALL QUESTIONS. Write your answers in the spaces provided in this booklet. If you need more space for answers, ask the Supervisor for extra paper. Write your SPIN on all extra sheets used and clearly number the questions. Attach the extra sheets at the appropriate places in this booklet.

Major Learning Outcomes (Achievement Standards)

Skill Level & Number of Questions Weight/

Time Level 1

Uni-structural

Level 2 Multi-

structural

Level 3 Relational

Level 4 Extended Abstract

Strand 1: Mechanics Demonstrate understanding of the physical phenomena, concepts, principles and relationships involved in mechanics

7 4 3 - 24%

62min

Strand 2: Waves Demonstrate understanding of the physical phenomena, concepts, principles and relationships related to waves

3 2 1 1 14%

36min

Strand 3: Electricity and Electromagnetism Demonstrate understanding by explaining and solving problems related to the physical phenomena, concepts, principles and relationships involved in electricity and electromagnetism.

5 3 2 1 21%

54min

Strand 4: Atomic and Nuclear Physics Demonstrate understanding of the physical phenomena, concepts, principles and relationships involved in Atomic and Nuclear Physics

2 1 1 1 11%

28min

TOTAL 17 10 7 3 70%

180 min Check that this booklet contains pages 2-16 in the correct order and that none of these pages is blank.

HAND THIS BOOKLET TO THE SUPERVISOR AT THE END OF THE EXAMINATION.

QUESTION and ANSWER BOOKLET Time allowed: Three hours

(An extra 10 minutes is allowed for reading this paper.)

109/1

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STRAND 1: MECHANICS

1.1 MOMENTUM

When objects collide or explode, the sum of their momentum before the collision or explosion equals the sum of their momentum afterwards, provided there are no external forces acting on the objects.

1.1a Define momentum.

1.1b A car stops at a traffic light junction. When the light turns green, the car accelerates, increasing its speed from 0 to 5.2 ms-1 in 0.832 s. Show that the linear impulse experienced by a 70 kg passenger in the car is 364 kg ms-1.

1.1c Calculate the average force experienced by the same passenger.

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1.1d A 90 kg fullback running east with a speed of 3 ms-1 is tackled by a 95 kg opponent

running west with a speed of 5 ms-1.

If the collision is perfectly inelastic, describe the collision qualitatively.

1.1e Explain the need for air bags in vehicles with respect to the concepts of impulse and

momentum.


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1.2 CIRCULAR AND ROTATIONAL MOTION

π = 3.14

Sarah stands on a platform that is rotating at a speed of 1.0 rev s-1 . Her arms are outstretched

and she holds a weight in each hand. The total rotational inertia of the system of Sarah, weights,

and platform is 6.0 kg m2.

1.2a In the space provided, draw a diagram to show the measure of 1 radian.

1.2b Identify the source of force providing the rotational motion of the system.

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1.2c By drawing the weights in towards her body, Sarah increases her angular speed to 19 rad s-1.

Explain why the angular speed increases.

1.2d Calculate the rotational inertia of the system after the weights have been drawn in.

1.2e One of the quantities used to describe rotational motion is angular displacement,𝜃,

and is measured in radians.

Convert 32⁰ to radians.


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1.3 SIMPLE HARMONIC MOTION The acceleration due to gravity = 9.80 m s-2 A pendulum bob swings between two points that are 2.8m apart. The period of the motion is 1.6 s.

1.3a Describe the oscillation of the pendulum bob in terms of its amplitude and its frequency assuming the movement of the bob is SHM.

1.3b

Write an equation that shows that the maximum acceleration of the pendulum bob is 22 ms-2.

1.3c

Write an equation that shows that the maximum velocity of the pendulum bob is 5.5 ms-1.

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2.8 m

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1.3d For the above pendulum to start swinging, energy must be supplied to begin the

motion. During each cycle of the swing of the pendulum bob, the energy changes

from kinetic energy, Ek to potential energy, EP.

On the diagram, mark and label, during the motion, where the pendulum bob

possesses kinetic energy (Ek), potential energy (Ep) and where it could possibly

possess both (both).

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STRAND 2: WAVES

2.1 MUSICAL NOTES

A musical note is produced when a standing wave is set up in the taut string of a stringed instrument or the pipe of a wind instrument. To set up a standing wave, a travelling wave must first be generated; by plucking the string of a stringed instrument or by ‘blowing’ into a wind instrument.

2.1a How is a standing wave formed?

2.1b Ben’s guitar string is 0.65 m long. The frequency of the fundamental mode is 85 Hz.

Calculate the wavelength of the standing wave.

2.1c On the diagram, draw the shape of the standing wave for second harmonic. Label one node (N) and one antinode (A).


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2.1d Radio waves are transverse waves which travel at the speed of light,

3.0 x 108 ms-1. Radio Hauraki broadcasts on its FM network in Auckland using a

radio wave of 99 MHz. National Radio broadcasts on its AM network in Auckland

using a radio wave of 756 kHz.

Calculate the wavelength of the radio used by Radio Hauraki.

2.1e A sound wave in water has a frequency of 500 Hz and a wavelength of 3.0m. Determine the speed of sound in water.

2.1f In a school talent show, a violin is plucked and plays the same note as the guitar, producing the same frequency. The violin is the highest sounding instrument in the violin family. Explain why the note from the violin sounds different from the note from the guitar.


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2.1g There are three ways to alter the note produced by a guitar string. These are:

1. Change the length of the vibrating string with your finger.

2. Change the tension force in the string by turning the tuning pegs.

3. Changing the heaviness (mass per metre) of the string.

With reference to either wave speed or wavelength (or both), discuss how each of

the above factors affect the frequency of a stretched guitar string.


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STRAND 3: ELECTRICITY AND ELECTROMAGNETISM

3.1 DC CIRCUITS AND CAPACITANCE

3.1a Define capacitance.

3.1b List two uses of capacitors.

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3.1c State Ohm’s Law.

3.1d One day Edward charged a 0.10 F capacitor up to 12V. He then discharged it

through a 25 Ω resistor.

How long would it take for the voltage across the capacitor to drop to

approximately 4.4 V and relate the significance of this time to the time

constant, 𝜏?


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3.2 ELECTROMAGNETIC INDUCTION

Michael Faraday (1791 – 1867) discovered that current can be induced by a changing magnetic

field using a set - up similar to that shown below.

3.2a Describe how this set-up works in producing an induced emf (electromotive force). Include expected observations along the progression of the experiment.

3.2b Define inductance.


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3.2c Explain how a transformer works.

3.2d Discuss how various modern safety features in electric circuits work, with an emphasis on how induction is employed.

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3.3 MAGNETIC FIELD

Some animals, such as pigeons, can detect the Earth’s magnetic

field and use it to navigate. Scientists are not sure how they do this,

but these creatures seem to have magnetic material in their bodies

that act like a compass.

3.3a Define magnetic field.

3.3b

Draw magnetic field lines around the single bar magnet shown.

3.3c

A school laboratory generator that is made from a

rectangular coil, 5 cm by 4 cm, is placed in a

magnetic field of strength 0.2 T. The coil rotates at

50 revolutions per second.

At the position shown in the diagram, the magnetic field is perpendicular to the

coil.

How much magnetic flux passes through at every turn?


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Strand 4: Atomic and Nuclear Physics

4.1 RADIOACTIVITY

The New Zealand Physicist, Ernest Rutherford (1871 – 1937) showed that there are three types of

radioactivity (radiation) namely alpha particle emission, beta particle emission and gamma

emission.

4.1a Compare and contrast the three types of radiation in terms of their traveling

speed, penetrating power and the effect of a magnetic field on each of them.

4.1b Define nuclear fusion.

4.1c Define nuclear fission.


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4.1d A large nucleus can disintegrate spontaneously by emitting any of the two particles

(alpha and beta) accompanied by gamma waves.

For instance, Radium, Ra, atomic number 88, and mass number 226, is a

radioactive chemical element discovered by Marie Curie in 1898. It emits an alpha

particle and gamma rays, and thereby changes into another element, Radon, Rn.

Write the balanced nuclear reaction described above.

4.1e Discuss processes to achieve practical fusion energy generation and suggest

safety measures necessary to minimise danger.

THE END

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