902550

2SUPERVISOR’S USE ONLY

9 0 2 5 5

© 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

2

Physics 90255, 2011

ASSESSOR’S USE ONLY

(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.

3

Physics 90255, 2011

ASSESSOR’S USE ONLY

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

4

Physics 90255, 2011

ASSESSOR’S USE ONLY

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.

5

Physics 90255, 2011

ASSESSOR’S USE ONLY

(e) ExplainhowtheforceexertedbytheballonJacquieandherbikeisdependentonthedurationofthetimeonimpact,ANDexplainhowtheforceexertedbytheballonJacquieandherbikeisrelatedtotheforceexertedbyJacquieandherbikeontheball.

�

Physics 90255, 2011

ASSESSOR’S USE ONLY

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.

7

Physics 90255, 2011

ASSESSOR’S USE ONLY

(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.

8

Physics 90255, 2011

ASSESSOR’S USE ONLY

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.

9

Physics 90255, 2011

ASSESSOR’S USE ONLY

10

Physics 90255, 2011

ASSESSOR’S USE ONLY

QUESTION NUMBER

Extra space if required.Write the question number(s) if applicable.

90

25

5