Level 2 Physics (90255) 2011 - New Zealand … ONE: THE BIKE RIDE (a) ... Will the ball hit Ernie or...
Transcript of Level 2 Physics (90255) 2011 - New Zealand … ONE: THE BIKE RIDE (a) ... Will the ball hit Ernie or...
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© New Zealand Qualifications Authority, 2011. All rights reserved.No part of this publication may be reproduced by any means without the prior permission of the New Zealand Qualifications Authority.
Level 2 Physics, 201190255 Demonstrate understanding of mechanics
2.00 pm �ednesday 1� November 2011pm �ednesday 1� November 2011 �ednesday 1� November 20111� November 2011 November 2011 Credits: Six
Check that the National Student Number (NSN) on your admission slip is the same as the number at the top of this page.
You should attempt ALL the questions in this booklet.
Make sure that you have Resource Sheet L2–PHYSR.
In your answers use clear numerical working, words and / or diagrams as required.
Numerical answers should be given with an appropriate SI unit.
If you need more room for any answer, use the extra space provided at the back of this booklet.
Check that this booklet has pages 2 – 10 in the correct order and that none of these pages is blank.
YOU MUST HAND THIS BOOKLET TO THE SUPERVISOR AT THE END OF THE EXAMINATION.
ASSESSOR’S USE ONLY Achievement Criteria
Achievement Achievement with Merit Achievement with ExcellenceIdentify or describe aspects of phenomena, concepts or principles.
Give descriptions or explanations in terms of phenomena, concepts, principles and / or relationships.
Give concise explanations that show clear understanding in terms of phenomena, concepts, principles and / or relationships.
Solve straightforward problems. Solve problems. Solve complex problems.
Overall level of performance
You are advised to spend �0 minutes answering the questions in this booklet.
All formulae are provided on the separate Resource Sheet L2-PHYSR.
QUESTION ONE: THE BIKE RIDE
(a) Jacquie is a bike rider. One morning she starts riding from rest and accelerates at 1.2 m s–2 for 14 seconds.
Showthatherfinalvelocityafter14secondsis16.8ms–1.
(b) SheheadsEastataconstantspeedof16.8ms–1, then turns left (heads North), without changing speed.
Draw a vector diagram and use it calculate the change in her velocity (size and direction).
N
S
W E
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(c) Jacquietakesherbikeonaboatacrossariver65mwide.Theboatheadsstraightacross(↑)theriver,withaspeedof6.8ms–1relativetothewater.Thecurrent(→)causestheboattoland15mdownstream.
Calculatethespeedoftheboatrelativetothebank(ground).
Youmaybeginyouranswerbydrawinglabelledvectordiagramsfordistancesandspeeds.
(d) Jacquie then rides along a horizontal circular path at constant speed.
Describewhatitisthatprovidestheforce needed to keep the bike going in a circle.
State the direction of this force.
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QUESTION TWO: THE BRIDGE
Jacquiecyclesalongauniformbridgethatissupportedatbothends,asshowninthediagram.
5.0 m
25.0 m
A B
(a) Thelengthofthebridgeis25.0m.ThemassofJacquieandherbikeis72kg.Themassofthebridgeis760kg.
Calculate the support force (FA)providedbyend A and the support force (FB) providedby end BofthebridgewhenJacquieis5.0mfromendA.
(b) Expressyouranswerstopart(a)tothecorrectnumberofsignificantfigures.
Giveareasonforyourchoiceofsignificantfiguresinyouranswerstopart(a).
(c) WhileJacquieiscyclingataspeedof16.8ms–1, she collides with a soccer ball that is rolling towardsherataspeedof8.0ms–1.Thesoccerballbouncesoffintheoppositedirectionwithaspeedof5.0ms–1.
16.8 m s–1
8.0 m s–1 5.0 m s–1
before collision after collision
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CalculateJacquie’svelocity(sizeanddirection)afterthecollision.
You may ignore any effects of friction.
MassofJacquieandherbike=72.0kg
Massofsoccerball=0.430kg.
(d) Explainwhatismeantbyanelastic collision and an inelastic collision.
Elastic collision:
Inelastic collision:
Describewhatyouwouldneedtodoinordertodeterminewhetherthiscollisionbetweenthebike and the soccer ball is elastic or inelastic.
You are not required to carry out any calculations.
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(e) ExplainhowtheforceexertedbytheballonJacquieandherbikeisdependentonthedurationofthetimeonimpact,ANDexplainhowtheforceexertedbytheballonJacquieandherbikeisrelatedtotheforceexertedbyJacquieandherbikeontheball.
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QUESTION THREE: ENERGY AND PROJECTILE MOTION
Jacquie’sbrotherErnieispushingalawnmowerwithaforceof26Natanangleof34° to the ground, as shown below.
www.treehugger.com/push-mower-jjh01.jpg
(a) Explainfullywhynotallofthe26NforceexertedbyErnieisusedtopushthelawnmowerhorizontallyalongtheground.
(b) CalculatethepowerproducedbyErniewhenheacceleratesthemowerthroughadistanceof4.0min3.0seconds.
Givethecorrectunitsforyouranswer.
For copyright reasons, this resource cannot be reproduced here.
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(c) Ernie’ssonJacobkicksaballtowardsErnieinthegarden.Ernieis1.75mtall.Jacobkickstheballwithavelocityof24ms–1atanangleof36°totheground.Jacobisstanding35mawayfromErnie.
36°
35 m
1.75 m
Jacob
24 m s–1
Ernie
Diagram is NOT to scale
WilltheballhitErnieorgooverhishead?
Inyourcalculations,startbyshowingthatthehorizontalcomponentoftheinitialvelocityofthe ball is 19.4 m s–1.
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Aspiderspinsawebinthegardenandamothgetscaughtintheweb.Thewebstretchesdownwardsby0.065mwhenthemothofmass0.003kgiscaughtinit.
Agraphforforceagainstextensionforthespider’swebisshownbelow.
force (N)
extension (m)
(d) ExplainwhytheformulaW = Fdcannotbeusedtocalculatetheelasticpotentialenergystored in the web when the moth gets caught in it.
Yourexplanationshouldincludeastatementofwhatshouldbeusedtocalculatethisenergy.
(e) Calculatetheelasticpotentialenergystoredinthewebwhenthemothiscaughtintheweb.
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QUESTION NUMBER
Extra space if required.Write the question number(s) if applicable.