JAMES RUSE AGRICULTURAL HIGH SCHOOL

JRAHS Physics Year 11 Half Yearly Assessment Task - Term 2 2012 page: 1

JAMES RUSE AGRICULTURAL HIGH SCHOOL

Student No. ……...........................…..

Half-Yearly Assessment Task

TERM 2, 2012

PHYSICS Theory Paper

General Instructions

Reading time – 5 minutes

Working time – 50 minutes

Write using black or blue pen

Draw diagrams using pencil

Write your Student Number on the Part A Answer Sheet and the Part B Question and Answer book

Total marks for this paper – 570

The Theory paper has two Parts: A and B

Part A Total marks 12

Attempt all questions

Allow about 12 minutes for this part

Part B Total marks 45

Attempt all questions

Allow about 38 minutes for this part


PART A: Multiple Choice

1. A car travels 40.0 km due south then 40.0 km due west.

What is the magnitude and direction of the car’s displacement?

Magnitude Direction

(A) 80.0 km West

(B) 56.6 km West

(C) 56.6 km South West

(D) 80.0 km South West

2. Which one of the following is a scalar and vector quantity respectively?

(A) Impulse and Power

(B) Energy and Momentum

(C) Force and Acceleration

(D) Mass and Time

3. A swimmer who is able to swim at 1 m s-1

, wishes to arrive at a point directly

opposite her starting point when she crosses a river which is flowing at 0.6 m s-1

East . In which direction must she head and what will be her resultant speed?

(A) and √ m s-1

(B) and √ m s-1

(C) and √ m s-1

(D) and √ m s-1

4. A ball thrown vertically upwards from the ground takes 2 s to reach maximum height.

Assuming there is substantial vertical air drag on the ball, how does the time of flight

for the upward journey compare with that of the downward journey?

(A) It takes 2 s to come down.

(B) It takes less than 2 s to come down.

(C) It takes more than 2 s to come down.

(D) It takes substantially more than 2 s to come down.

5. The kinetic energy of a 4 kg object is . What is the kinetic energy of an 8 kg object

which moves at twice the speed of the 4 kg object?

(A)

(B)

(C)

(D)


6. Modern automobiles are tested for collision safety using models of human beings

often called crash test dummies. These "dummies" are actually quite "smart." They

are often fitted with sensor devices that can record their motion and force of impact

during an automobile collision.

When the car accelerates from a standing start, the crash test dummy appears to be

pressed backward into the seat cushions. Which of the following best explains why

this happens?

(A) The crash test dummy gets lighter as the car accelerates.

(B) The car is moving forward faster than the crash test dummy.

(C) There is no reaction to the force of the car taking off.

(D) Gravity is pulling the crash test dummy in the direction the car is moving.

7. Two identical spring-balances P and Q are connected by pieces of string to a fixed

wall as shown below.

A horizontal force of 100 N is exerted on spring-balance Q.

What will be the reading on spring-balances P and Q?

(Assume that the weight of the balances and the string is negligible and that the

system is stationary.)

Spring-balance P Spring-balance Q

(A) 0 N 100 N

(B) 200 N 200 N

(C) 50 N 50 N

(D) 100 N 100 N

wall

Q P


8. A ball is thrown out of the passenger window of a car moving to the right (ignore air

resistance). If the ball is thrown out perpendicular to the velocity of the car, which of

the following best depicts the path the ball takes, as viewed from a stationary observer

above?

(A)

(B)

(C)

(D)


9. Two blocks of masses 3 kg and 2 kg, connected by a light inextensible string are

resting on a smooth horizontal surface. A horizontal force of 10 N is applied to the

right as shown in the diagram below.

Assuming the system moves to the right, what is the tension, T in the string and the

acceleration, of the system?

Tension, T

(N)

Acceleration, a

(ms-2

)

(A) 4 2

(B) 15 5

(C) 6 2

(D) 10 5

10. Circular waves are created in a sink full of water by repeatedly dipping your finger.

What happens to the wavelength, frequency and speed of the wave as you move your

fingers faster?

Wavelength Frequency Speed

(A) Increases Decreases Stays the same

(B) Stays the same Increases Decreases

(C) Decreases Increases Stays the same

(D) Stays the same Decreases Increases

3 kg 10 N 2 kg

T


11. The diagram below shows a transverse travelling wave in a string. The wave is

moving from right to left and a particular moment in time ( is shown. At the

moment shown, point has a displacement of zero and point has a maximum

displacement.

Which one of the following gives the ensuing direction of motion of point and ?

(A) moves downwards, moves upwards

(B) moves downwards, moves left

(C) moves upwards, moves upwards

(D) moves left, moves right

12. Compressions and rarefactions are characteristics of sound waves. Which statement is

correct?

(I) A compression is a volume of increased air pressure.

(II) A rarefaction is a volume of reduced air pressure.

(III) Compressions and rarefactions correspond to troughs and crests respectively

of a transverse wave.

(A) (I) only

(B) (II) only

(C) (I) and (II) only

(D) (I) and (III) only


Student Number : …………………

Part A Answer Sheet Total marks: 12

A B C D

1

2

3

4

5

6

7

8

9

10

11

12


PART B: Extended Response Marks

13. A car with mass 1500 kg is travelling at 60 km h-1

, east. It collides head on with an

identical car travelling at 80 km h-1

in the opposite direction. Assume the cars lock

together and move off as a combined wreck.

(a) Find the velocity of the wreck immediately after the collision. (3)

( … (law of conservation of linear momentum)

(

(West)

(b) Is kinetic energy conserved in this situation? Justify your reasoning, without the use

of calculations. (2)

No, as the collision is inelastic (since the cars lock together).


Marks

14. A hot-air balloon is rising vertically at a speed of 10 m s-1

. An object is released

from the balloon. The graph shows how the velocity of the object varies with time

from the time it leaves the balloon to the time it reaches the ground four seconds

later. It is assumed that the air resistance is negligible.

(a) Use the graph to show that the object continues to rise for a further 5 m after it is

released from the balloon. (2)

Time taken to reach maximum height is 1 s, at which time its speed is zero. Hence

from the graph, the displacement in the first second is given by the area under the

curve from

i.e. Displacement =

-40

-30

-20

-10

10

20

Velocity ( m/s)

0 Time (s) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5


Marks

(b) Determine the total distance travelled by the object from the time it is released

until it hits the ground. (2)

Total distance = area under graph =

(

(c) Hence determine the object’s final displacement from its point of release from the

balloon. (2)

Final displacement =

( ( ( )

(d) Use the axes below, sketch a graph showing the object’s acceleration as a function

of time from the time it leaves the balloon to the time it lands on the ground.

Include any critical values on the axes. (2)

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Time (s)

Acceleration ( m/s2)


Marks

15. Consider a car rounding a flat curve, as shown below.

(a) Indicate on the diagram, all the forces acting on the car at the instant it rounds the

bend. Provide the name and direction of the force/s. (3)

(b) Suppose a car rounds a circular bend and takes 3.5 minutes to go once around.

Determine at what speed the car travels around the bend, if the radius of the bend is

360 m (2)

Hence speed of car is 11 m/s (2 sf) or 39 km/h

(c) Calculate the magnitude and direction of the acceleration of the car as it travels

around this bend. (2)

(directed towards the centre of the road/bend)

Normal/Reaction Force

Centripetal Force

Weight Force Driving Force

Drag/Air resistance


Marks

16. An elevator rises upwards with an acceleration of 2 m s-2

. A passenger of repute of

mass 60 kg is standing on a bathroom scale inside the elevator, as shown below.

(a) In the space provided draw a simple diagram to show all the forces acting on the

passenger. (2)

(b) What is the reading on the bathroom scale (in N) as the elevator accelerates upwards?

Justify your reasoning with calculations. (2)

But by Newton’s 2nd

law

(

(

Hence reading on bathroom scale is 708 N

(c) Assuming that the cables supporting the elevator were to snap, what will be the

reading on the bathroom scale? (1)

Zero

DIAGRAM

Normal force

Weight


Marks

17. A black billiard ball which is struck head on by a white cue ball drops into the pocket

of the billiard table. The cue ball remains stationary after striking the black ball.

(a) Explain, using relevant physics principles why the cue ball remains stationary after

striking the black ball. (2)

Since the collision is perfectly elastic, both linear momentum and kinetic energy are

conserved. Hence all the momentum and kinetic energy are transferred to the black

ball, resulting in the cue ball being stationary after the collision.

(b) If the cue ball was in contact with the black ball for 0.03 s, while a constant force of

100 N was exerted on the black ball, determine the speed with which the cue ball

struck the black ball. Assume the mass of each of the balls is 170 g. (2)

(

(

Hence speed of the cue ball just before impact is 17.6 m/s


Marks

18. A 1200-kg car accelerates uniformly from 5.0 m s-1

east to 12.0 m s-1

east in 2.0 s.

During this time the car travels 17.0 m.

(a) Calculate the average acceleration during this time interval. (2)

(b) Determine the net force acting on the car during this time interval. (1)

(c) If the car experiences a constant retarding force of 200 N, calculate the work done by

the engine during this time. (2)

19. Identify one safety feature in cars and explain using the relevant Physics principles

how its purpose is satisfactorily achieved. (3)

* Airbags/seatbelts/crumple zones/side impact beams/ABS brakes, traction control

* Physics principle

* How achieved

E.g.

Airbags are deployed during a sudden change in motion of a vehicle. The airbags

form a barrier between the passenger and the dashboard/windscreen. The impulse or

change in momentum imparted to the passenger remains the same. However from

, the time the passenger is in contact with the airbag is

substantially increased, thereby reducing the contact force, and eventually reducing

the probability of serious injury.


Marks

20. State, using a flow diagram, the energy transformations that occur in any one of the

following devices:

(i) mobile phone

(ii) television

(iii) fax/modem (2)

(i) Mobile phone:

(ii) Television:

(iii) Fax/modem:

21. Inertia can be dangerous for a car either at rest or when moving. Describe two ways in

which the danger may arise for each case. (2)

If the car at rest is struck by another vehicle at the rear, then by Newton’s first law

(inertia), the passenger will tend to remain at rest, while the car moves forward due to

the impact. The reaction to this forward motion results in a reverse force on the

passenger, causing whiplash (neck/back injury), hence the danger.

For a car that is moving forward, and struck by another car from the front, the

passengers tend to continue to move forward due to the law of inertia. This causes the

passengers to either crash into the dashboard/windscreen/airbags, resulting in injury.


22. A student is studying water waves. The variation with time of the displacement of

a particle in the wave is shown below.

The distance of the oscillating particles from the source of the waves is measured. At a

particular time, the variation of the displacement with distance is shown below.

For the water wave, determine the

(a) period of vibration, (1)

(b) wavelength, (1)

(c) speed, (2)

END OF EXAM

JAMES RUSE AGRICULTURAL HIGH SCHOOL

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