05 Elasticity

46 minutes

46 marks

Q1.          A 1 N weight is tied to a 30 cm long piece of elastic. The other end is fixed to the edge of a laboratory bench. The weight is pushed off the bench and bounces up and down on the elastic.

          The graph shows the height of the weight above the floor plotted against time, as it bounces up and down and quickly comes to rest.

(a)     Mark on the graph a point labelled F, where the weight stops falling freely.(1)

(b)     Mark on the graph a point labelled S, where the weight finally comes to rest.(1)

(c)     Mark two points on the graph each labelled M, where the weight is momentarily stationary.(1)

(Total 3 marks)

 

 

Q2.         When a bungee-jump is made the jumper steps off a high platform. An elastic cord from the platform is tied to the jumper.The diagram below shows different stages in a bungee-jump.Forces A, B and C are forces acting on the jumper at each stage.

moving down                  moving down                  moving downlarge acceleration           small acceleration        slowing acceleration

  diagram X                      diagram Y                       diagram Z

(a)     Name force A.

....................................................................................................................................(1)

(b)     The motion of the jumper is shown in the diagrams.By comparing forces A, B and C, state how the motion is caused in:

(i)      diagram X;

............................................................................................................................

(ii)     diagram Y;

............................................................................................................................

(iii)     diagram Z.

............................................................................................................................

(3)

(c)     The table gives results for a bungee cord when it is being stretched.

STRETCHING FORCE (N) 100 200 400 600 800

LENGTH OF CORD (m) 20 24 32 40 48

(i)      Plot a graph of these results on the graph paper.

(3)

(ii)     Use the graph to find the length of the cord before it was stretched.

Length .................... m(1)

(Total 8 marks)

 

 

Q3.          The diagrams show pairs of forces acting on different objects. In each case describe what happens when the forces are increased. Then describe what happens when the forces are removed.

(a)

          When the forces are increased ...................................................................................

....................................................................................................................................

          When the forces are removed ....................................................................................

....................................................................................................................................(2)

(b)

          When the forces are increased ...................................................................................

....................................................................................................................................

          When the forces are removed ....................................................................................

....................................................................................................................................(2)

(Total 4 marks)

 

 

Q4.          (a)     The diagrams below show pairs of forces acting on different objects. In each case describe what happens when the forces are increased. Then describe what happens when the forces are removed.

(i)     

         When the forces are increased

...........................................................................................................................

...........................................................................................................................

         When the forces are removed

...........................................................................................................................

...........................................................................................................................

(ii)

         When the forces are increased

...........................................................................................................................

...........................................................................................................................

         When the forces are removed

...........................................................................................................................

...........................................................................................................................

(iii)

         When the forces are increased

...........................................................................................................................

...........................................................................................................................

         When the forces are removed

...........................................................................................................................

...........................................................................................................................(6)

(b)     The graph shows the increase in length of a spring against load (force).

          The length of the spring with no load was 15 cm.

          Use the graph to find:

(i)      The load needed to produce an increase in length of 2 cm.

         ...........................................................................................................................

(ii)     The increase in length produced by a load of 2.3 N.

         ...........................................................................................................................

(iii)     The length of the spring when the load was 2.3 N.

         ...........................................................................................................................(3)

(Total 9 marks)

 

 

Q5.          (a)     The pictures show four objects. Each object has had its shape changed.

          Which of the objects are storing elastic potential energy?

.....................................................................................................................................

          Explain the reason for your choice or choices.

.....................................................................................................................................

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.....................................................................................................................................(3)

(b)     A student makes a simple spring balance. To make a scale, the student uses a range of weights. Each weight is put onto the spring and the position of the pointer marked

                    

          The graph below shows how increasing the weight made the pointer move further.

(i)      Which one of the following is the unit of weight?.

Draw a ring around your answer.

          joule           kilogram             newton                  watt(1)

(ii)     What range of weights did the student use?

...........................................................................................................................(1)

(iii)     How far does the pointer move when 4 units of weight are on the spring?

...........................................................................................................................(1)

(iv)    The student ties a stone to the spring. The spring stretches 10 cm.

         What is the weight of the stone?

...........................................................................................................................(1)

(Total 7 marks)

 

 

Q6.The diagram shows a strain gauge, which is an electrical device used to monitor a changing force.

Applying a force to the gauge causes it to stretch.This makes the electrical resistance of the wire change.

 

 

 

 

 

(a)     (i)      Using the correct symbols, add to the diagram to show how a battery, an ammeter and a voltmeter can be used to find the resistance of the strain gauge drawn above.

(2)

(ii)     When in use, the strain gauge is always connected to a d.c. power supply, such as a battery.

How is a d.c. (direct current) power supply different from an a.c. (alternating current) power supply?

...............................................................................................................

...............................................................................................................

...............................................................................................................(1)

(b)     Before any force is applied, the unstretched gauge, correctly connected to a 3.0 V battery, has a current of 0.040 A flowing through it.

(i)      Use the equation in the box to calculate the resistance of the unstretched gauge. 

potential difference    =    current    ×    resistance

Show clearly how you work out your answer.

...............................................................................................................

...............................................................................................................

                        Resistance = ............................................................ Ω(2)

(ii)     Stretching the gauge causes the current flowing through the gauge to decrease.

What happens to the resistance of the gauge when it is stretched?

...............................................................................................................

...............................................................................................................(1)

(iii)    What form of energy is stored in the gauge when a force is applied and the gauge stretches?

...............................................................................................................(1)

(Total 7 marks)

 

 

Q7.          A student investigated how the extension of a spring depends on the force applied to the spring.

The diagram shows the spring before and after a force had been applied.

(a)      (i)     Complete the following sentence using letters, A, B, C or D, from the diagram.

The extension of the spring is the distance between the positions labelled

......................and ...................... on the metre rule.(1)

(ii)     What form of energy is stored in the stretched spring?

...............................................................................................................(1)

(b)     The results from the investigation are plotted on the following graph.

(i)     The graph shows that the student has made an error throughout the investigation.

What error has the student made?

...............................................................................................................

...............................................................................................................

Give the reason for your answer.

...............................................................................................................

...............................................................................................................(2)

(ii)     The student has loaded the spring beyond its limit of proportionality.

Mark on the graph line the limit of proportionality of the spring. Label the point P.

Give the reason for choosing your point P.

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(c)     The student uses a different spring as a spring balance. When the student hangs a stone from this spring, its extension is 72 mm.

The spring does not go past the limit of proportionality.

Calculate the force exerted by the stone on the spring. 

spring constant = 25 N/m

Use the correct equation from the Physics Equations Sheet.

Show clearly how you work out your answer.

........................................................................................................................

........................................................................................................................

                                           Force = .................................................. N(2)

(Total 8 marks)

 

  

M1.          (a)     F 50 cm on first part of graphtolerance + or – 3cm

1

(b)     S at the far rightcredit anywhere to right of last trough

1

(c)     M on any two tops of peaks or bottoms of troughsboth are required for the mark M needs to be central to the troughor peak, except if F is in the way in one case

1[3]

 

 

M2.          (a)     weight or gravity or gravitationalfor 1 mark

1

(b)     (i)      only force A acts / force A > air resistance / gravity / weightfor 1 mark

1

(ii)     force A > force Bfor 1 mark

1

(iii)     force C > force Afor 1 mark(Forces A, B and C need not be used, description of forces are OK)

1

(c)     (i)      graph points all correct ± little squaregains 2 marks

         one point wronggains 1 mark

         2+ points wronggains 0 mark

         appropriate line – good freehand OKgains 1 markBar chart gets 0, but if points clear can get 2

3

(ii)     16 or candidates own intercept should be 16 m in range 1-19if no kinks on graph linefor 1 mark

1[8]

 

 

M3.          (a)     plasticine stretches/snapsstays stretched/snapped/same

for 1 mark each2

(b)     spring compresses OWTTEreturns to original length/gets longer

for 1 mark each2

[4]

 

 

##

          (a)     (i)      plasticine stretches/snapsstays stretched/snapped

for 1 mark each2

(ii)     spring compresses OWTTEreturns to original length/shape or gets longer

for 1 mark each2

(iii)     ruler bends/breaksreturns to original shape or stays broken

for 1 mark each2

(b)     (i)      1.5Nfor 1 mark

1

(ii)     4 cmfor 1 mark

1

(iii)     19 cmfor 1 mark

1[9]

 

 

M5.          (a)     B or bungee cords1

          C or springs or playground rideeach additional answer loses 1 mark minimum mark zero

1

          will go back to original shape/size1

(b)     (i)      newton1

(ii)     0 – 5 (N) or 5accept1 – 5 (N)do not accept 4

1

(iii)     16 (cm)1

(iv)    2.5 (N)accept answer between 2.4 and 2.6 inclusive

1[7]

 

 

M6.         (a)      (i)     ammeter and battery in series with the gaugesymbols must be correctignore a voltmeter drawn in series

or cells reversed to cancel out1

voltmeter in parallel with the gaugesymbol must be correctaccept a freestanding circuitdiagram provided strain gauge is labelled or a resistor symbol used for the strain gauge

1

(ii)     d.c. flows only in one directiona.c. changes direction is insufficient

1

(b)     (i)      75this answer onlyallow 1 mark for correct substitution and transformation,

ie resistance = 

2

(ii)     increases1

(iii)    elastic / strain potentialdo not accept potential

1[7]

 

M7.         (a)       (i)     B Ceither order

1

(ii)     elastic potential (energy)accept strain for elastic

1

(b)     (i)     mark both parts together1

measured / recorded the length of the spring (and not extension)accept measured A–C (and not B–C)accept did not work out/measure the extension

extension does not equal zero when force = 0accept line should pass through the origin

1

(ii)     point marked at 5.5 (N)accept any point between 5.0 and 5.6 inclusive

1

up to that point force and extension are (directly) proportionalaccept it’s at the end of the straight part (of the graph line)accept past that point force and extension are no longer (directly) proportionalaccept the line starts to curve

1

(c)     1.8allow 1 mark for correct substitution, ie 25 x 0.072 provided no subsequent step shownan answer 1800 gains 1 markan incorrect conversion from mm to m with a subsequent correct calculation gains 1 mark

2[8]

 

 

E1.          The understanding of the graph was poor. Few candidates knew the point at which the weight stops falling freely.

 

 

E3.          Part (a) was very well answered with many candidates scoring four marks. In (a) very few attributed elastic properties to the plasticine, a few in (b) had the spring incorrectly extending, although scoring the second mark for returning to its original length.

 

 

E4.          Part (a) was very well answered with many candidates scoring six marks. In (i) very few attributed elastic properties to the plasticine, a few in (ii) had the spring incorrectly extending although scoring the second mark for returning to its original length. In (iii) the many scoring answers covered just about everything pupils can do with a plastic ruler in class, clearly many had learnt from experience. Part (b) proved to be more difficult, many had the force correct as 1.5N and the extension as 4cm, but the information that the unloaded length of the spring was 15cm appeared to have been missed by many and the answer to the final part of the question eluded these candidates.

 

 

E5.          In part (a) many candidates identified at least one elastic object, pleasingly few candidates thought A or D were elastic. However, fewer candidates were able to correctly say why they had made their choice. “Springy”, “stretchy” or a repetition of the question stem being the most popular responses.

(b)(i) and (b)(ii) Less than half of the candidates gave the correct answers.

(b)(iii) The majority of candidates could use the graph to obtain a correct answer.

(b)(iv) Just over half the candidates gave the correct answer.

 

 

E6.         (a)      (i)     Only about a fifth of candidates scored full marks, with a further two fifths of candidates scoring one mark, usually losing the mark for the misplacing of the voltmeter. Scripts with higher marks usually had candidates drawing the circuits with the use of a ruler. Perhaps using a ruler indicated they would be careful when drawing the components. The most common error was joining both the ammeter and voltmeter in series suggesting a lack of practical experience. Others placed the voltmeter across the wrong component or even across a lead, and some lost marks for careless diagrams, notably lines drawn through meters and gaps in the circuit.

(ii)     Just over half the candidates scored this mark. Many candidates believe that it is thevalue of d.c. which does not change, and many responses appeared based on the appearance of a.c. and d.c. on an oscilloscope. Another common incorrect response referred to d.c. going straight to the component.

(b)     (i)      Approximately three quarters of candidates completed the calculation correctly. Weaker candidates struggled to transform the equation.

(ii)     The relationship between current and resistance is, generally, well understood and four fifths of candidates scored this mark. Weaker candidates often used inappropriate language; the use of ‘stronger’ resistance was one such example. Candidates would benefit by using the stem to help their wording; if the word decrease is used in the stem it makes sense to respond with the word increase and not seek synonyms which are less appropriate.

(iii)    Many candidates realised that elastic energy is stored but under half of candidates gained the mark since many failed to include the word potential in their answer. The wrong answers often referred to kinetic energy.

 

 

E7.         (a)      (i)     This was poorly answered with only just over a tenth of students scoring the mark. The most popular incorrect answer was to give points A and C, the total length of the extended spring.

(ii)     Again this was very disappointing, only a fifth of students could give the correct form of energy stored in the spring.

(b)     (i)      There were very few correct answers to this question. The majority of the students seemed concerned that a couple of the points were not exactly on the line or that the straight line suddenly curved upward.

(ii)     Just over a quarter of students were able to place the letter P in the correct position on the graph line, of these students only half could give a correct reason for their choice. Most incorrect responses showed placement of the letter at either the last point recorded by the student, or at a point where the graph line reached the top of the grid of the graph paper.

(c)     A tiny proportion of students scored both marks in this question. However, about three-quarters were able to obtain a single mark. Unfortunately, the vast majority of the students failed to notice that the unit for the spring constant in the stem of the question was in

newtons per metre, and simply multiplied the spring constant by the extension which was in millimetres. When calculated correctly, these students and those who made errors in their unit conversion, were able to score one mark.