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A Level Physics A H556/03 Unified physics
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OCR A Level Physics A H556/03 Unified physics 2021
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PHYSICS PAPER 3Oxford Cambridge and RSA
Wednesday 20 October 2021 – Morning
A Level Physics A
H556/03 Unified physics
Time allowed: 1 hour 30 minutes
You must have:
* 8 3 3 4 5 3 1 4 5 9 *
• The Data, Formulae and Relationships Booklet
You can use:
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 5 5 6 0 3 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
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] OCR is an exempt Charity
DC (LEG/CT) 300234/5 Turn over
, 2
Answer all the questions.
1 Fig. 1 shows a high-speed electric train.
overhead cable
at +25 kV
sliding contact
II
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 × 105 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]
© OCR 2021
, 3
(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.
150
F / kN
100
50
30 40 50 60
v / m s–1
1. Use the graph to show that output power of the electric motor during this period is
constant at about 4 MW.
[3]
2. 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
© OCR 2021 Turn over
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