Int Nature Q 07

Name: _________________________________________ Teacher’s Code

New Zealand Institute of Physics

PHYSICS Level 2: 2007 90528 v2 Demonstrate understanding of physics in an integrated context Credits: Three Answer ALL the questions in the spaces provided.

If you need more space for any answer, use the pages provided at the back of this booklet and clearly number the question. For all numerical answers, full working should be shown and the answer should be rounded to the correct number of significant figures and given with an SI unit. For all ‘describe’ or ‘explain’ questions, the answer should be in complete sentences with all logic fully explained. YOU MUST HAND THIS BOOKLET TO THE SUPERVISOR AT THE END OF THE ASSESSMENT.

For Assessor’s use only

Achievement Criteria

Achievement Identify or describe aspects of phenomena, concepts or principles in an integrated context.

Achievement with Merit Give descriptions or explanations in terms of phenomena, concepts, principles and/or relationships.

Achievement With Excellence Give concise explanations that show clear understanding, in terms of phenomena, concepts, principles and/or relationships.

Overall Level of Performance

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

2 You may find the following information and formulae useful:

−

Acceleration due to gravity = 10 ms 2 (2sf)

1 1 1 = + f d o di

v=

∆d ∆t

m=

a=

∆v ∆t

∆ p = F∆ t

F = ma

τ = Fd

q I= t

F = Eq ΔE V= q

n1sinθ

vf = vi + at

p = mv

V E= d

di h = i do h o

= n2sinθ

d = vit + ½at2

EP = ½kx2

EK = ½mv2

F = −kx

ac =

∆ EP = Eqd V = IR

1

P = IV

v2 r

EK = ½mv2 ΔE P= t

n1 v 2 λ 2 = = n2 v1 λ 1

2

d=

vi + vf t 2

∆ EP = mg∆ h Fc =

v = fλ

vf2 = vi2 + 2ad

W = Fd

P=

W t

mv 2 r

F = BIL

F = Bqv

V = BvL

RT = R1 + R2 + ….

1 1 1 = + + ... R T R1 R 2

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

3 It is recommended that you take 50 minutes to complete this assessment. Annie and Brendan are sitting in the stand watching a game of tennis. QUESTION ONE One of the players is serving the ball. A serve is when the ball is thrown up into the air and then hit by the racquet so that it goes over the net and hits the ground on the other side. The diagram below shows the path of the ball from the instant it is hit by the racquet to when it hits the ground. 38 m s−1

net

The radar gun measures the speed of the ball, after it was served, at 38 ms -1. The radar gun measures the horizontal speed of the ball, but the ball leaves the racquet travelling downward at an angle of 4.50° to the horizontal. (a)

[i] Show that the vertical speed of the ball as it leaves the racquet has an unrounded value of 2.99066 ms-1. _________________________________________________________________ _________________________________________________________________ [ii] Round this value to the correct number of significant figures. _________________________________________________________________ Vertical speed = _______________________________

The ball follows a projectile path as it travels from the racquet to the ground on the opposite side of the net.

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

4 (b)

Assuming friction with the air can be ignored, explain why the path of the ball, while it is in the air, can be considered projectile motion. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

(c)

If the ball is in the air for 0.47 s calculate the height above the ground at which the ball left the racquet. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Height = _____________________________________

(d)

When the player serves the ball the force that is applied by the racquet strings against the ball causes the strings to stretch a bit. Explain the energy changes that take place while the ball is in contact with the racquet strings that cause the ball to travel forward off the racquet. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

5 The ball bounces up high and is hit by the receiver’s racquet in such a way that it travels back parallel to its incident path. The change in momentum of the ball is 2.3 kg ms-1.

−1

17 m s

23 m s−1

(e)

Draw an arrow on the diagram to show the direction of the change in momentum.

(f)

If the average force on the ball while it is in contact with the racquet is 410 N, calculate the time that the ball is in contact with the racquet. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Time = ______________________________________

(g)

Calculate the mass of the ball. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Mass = ______________________________________

The ball hits the strings of the racquet, but the player holds the racquet by its handle and so the impact of the ball on the racquet will try to make it pivot.

pivot

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

6 (h)

If the distance between the point of impact of the ball on the strings and the point on the handle at which the racquet tries to pivot is 0.55 m, calculate the torque of the ball on the racquet. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Torque = ____________________________________

(i)

Explain what the player must do to prevent the racquet from pivoting. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

7 QUESTION TWO Annie finds it helpful to listen to a radio broadcast of the match while she is watching it. The radio she is using does not require any batteries because her turning a handle generates the power it uses. The action of turning the handle causes a coil of wire to turn inside a magnetic field. The diagram below shows one turn of the coil. As the coil rotates a voltage is induced across PQ and across RS.

North

South Q

P

(a)

R

S

Explain why a voltage is not induced across QR. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

(b)

Explain why the voltage induced across PQ will be in series with (i.e. it will not oppose) the voltage induced across RS. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

8 The size of the magnetic field is 0.75 T, the dimensions of the loop are PQ = RS = 0.058 m, QR = 0.018 m, and the speed of PQ and QR as they rotate is 0.23 ms-1. (c)

Calculate the size of the voltage induced across one complete turn of the coil. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Voltage = ____________________________________

(d)

The mass of an electron is 9.11 × 10-31 kg. Calculate the centripetal force on each electron in PQ and RS of the coil. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Centripetal force = _____________________________

A simple representation of the electric circuit of the radio is shown. The resistance, R, includes the resistance of the coil and of the other components needed to ensure the radio, including all background lighting, is powered by a suitable current. When the resistance of R1 is set at its maximum value of 31 Ω the total resistance of the circuit is 29.2 Ω . 3.0 V

I

R 1.3 Ω

R1max = 31 Ω

R2

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

9

(e)

Show that the combined resistance of the two parallel resistors is 27.9 Ω . _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

(f)

Calculate the current, I, in the circuit. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Current = ____________________________________

(g)

Calculate the current through the 31 Ω resistor. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Current = ____________________________________

(h)

Calculate the resistance of the resistor R2. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Resistance = _________________________________

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

10 (i)

Explain what happens to the voltage across R when the resistance R1 is reduced. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

(j)

The upper part of the stand Annie is sitting in blocks the straight-line passage of the radio wave from the transmitter to her radio. Explain why the radio receives a radio wave from the transmitter but Annie’s eye does not receive a light wave from the transmitter. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

11 QUESTION THREE Brendan uses binoculars to get a better view of the action. Each side of the binoculars consists of an objective lens and an eyepiece lens. The following diagram (not to scale) is a simplified representation of the arrangement of the lenses.

eyepiece lens

objective lens

light from a distant point

objective image

(a)

If the focal length of the objective lens is 0.15 m calculate the image distance of a point on an object that is 15 m from the lens. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Image distance = ______________________________

To make the physical size of the binoculars as small as possible, prisms are used to cause multiple reflections between the objective lens and image. The diagram shows the principle of this arrangement.

(b)

The angle of incidence at each reflecting surface is 45°. If this is the critical angle calculate the refractive index of the material of the prisms. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Refractive index = _____________________________

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

12 The image created by the objective lens becomes the object of the eyepiece lens. (c)

Suggest a reason why the image created by the eyepiece lens should be virtual. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________

(d)

If the focal length of the eyepiece is 20 mm and the magnification is 8, calculate the distance of the objective image from the eyepiece lens (i.e. the object distance for the eyepiece lens). _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Object distance = ______________________________

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007

13 Question Number

If you need more space for any answer, continue here. Clearly number the question. _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________

90528 • Demonstrate understanding of physics in an integrated context • Question and Answer Booklet 2007