OCR 2021 [601/4743/X] DC (LEG/CT) 300234/5

Oxford Cambridge and RSA Please write clearly in black ink. Do not write in the barcodes.First name(s) Last name Centre numberCandidate number OCR is an exempt Charity Turn over

INSTRUCTIONS

• Use black ink. You can use an HB pencil, but only for graphs and diagrams.• Write your answer to each question in the space provided. If you need extra space use the lined pages at the end of this booklet. The question numbers must be clearly shown.• Answer all the questions.• Where appropriate, your answers should be supported with working. Marks might be given for using a correct method, even if your answer is wrong.

INFORMATION

• The total mark for this paper is 70.• The marks for each question are shown in brackets [ ].• Quality of extended responses will be assessed in questions marked with an asterisk (*).• This document has 20 pages.

ADVICE

• Read each question carefully before you start your answer.

© OCR 2021 [601/4743/X]

DC (LEG/CT) 300234/5

*H55603*

You must have:

• The Data, Formulae and Relationships Booklet

You can use:

• a scientific or graphical calculator • a ruler (cm/mm)

*8334531459*

Wednesday 20 October 2021 – Morning A Level Physics A H556/03 Unified physics

Time allowed: 1 hour 30 minutes

Your text here 1

2

© OCR 2021

Answer all the questions.

• Fig. 1 shows a high-speed electric train.

I I sliding contact overhead cable at +25 kV motor turning wheels earthed rails at 0 kV Fig. 1 The potential difference between the overhead cable and the rails on the ground is 25 kV.The sliding contact on the top of the train constantly touches the overhead cable.The overhead cable supplies a current I to the electric motor of the train.The motor turns the wheels. The train experiences a resultant forward force F.The total mass of the train is 2.1 × 10 5 kg.(a) The train accelerates from rest. The value of F is 190 kN for speeds less than 6.0 m s –1 .(i) Show that the train’s acceleration is about 1 m s –2 .[1] (ii) Calculate the distance s that the train travels to reach a speed of 6.0 m s –1 .s = ..................................................... m [2]

3 Turn over© OCR 2021 (iii) The speed of the train is v.During one period of its journey, the train accelerates from v = 30 m s –1 to v = 60 m s –1 .The graph of F against v for this period is shown below.

30 40 50 60

50 100 150 v / m s –1 F / kN

• Use the graph to show that output power of the electric motor during this period is

constant at about 4 MW.[3]

• Calculate the current I in the electric motor when the train is travelling at 50 m s

–1 .

I = ...................................................... A [2]

Question 1 is continued on page 4

4

© OCR 2021

(b) The overhead cable in Fig. 1 must be tensioned.It is constructed from several equal lengths of wire.Some data for one length of this wire are shown below.• length = 1500 m • area of cross-section = 1.1 × 10 –4 m 2 • resistivity = 1.8 × 10 –8 Ω m • the Young modulus = 1.2 × 10 10 Pa • strain = 1.3% (i) Calculate the resistance R of one length of wire.

R = ..................................................... Ω [2]

(ii) Calculate the tension T in one length of wire.

T = ..................................................... N [3]