The force resisting the motion of a car is proportional to the square of the car’s speed. The magnitude of the force at a speed of 20.0 m s-1 is 800 N.

Question 29

The force resisting the motion of a car is proportional to the square of the car’s speed. The magnitude of the force at a speed of 20.0 m s^-1 is 800 N.

What useful output power is required from the car’s engine to maintain a steady speed of

40.0 m s^-1?

A 32 kW                      B 64 kW                      C 128 kW                    D 512 kW

Reference: Past Exam Paper – November 2018 Paper 11 Q17

Solution:

Answer: C.

Resistive force F is proportional to v².

F ∝ v²

F = kv²             where k is a constant

From the question, when force F = 800 N when speed v = 20 m s^-1.

k = F / v² = 800 / 20² = 2

So, F = 2v²   

The power output P = Fv

Since F = 2v²,

Output power P = Fv = (2v²) × v = 2v³

When speed v = 40 m s^-1,

Output power P = 2 × 40³ = 128 000 W = 128 kW

• 9702 November 2012 Paper 11 Worked Solution | A-Level Physics

1 B                  11 C                21 D                31 B

2 C                  12 A                22 D                32 A

3 D                  13 A                23 A                33 C

4 B                  14 A                24 B                34 D

5 B                  15 B                25 B                35 C

6 C                  16 B                26 D                36 C

7 A                  17 C                27 A                37 B

8 D                  18 A                28 B                38 C

9 A                  19 A                29 C                39 A

10 C                20 C                30 B                40 B

6 - Ans: C. See solution 433 at
A quantity X varies with temperature θ as shown. θ is determined from the corresponding values of X by using this graph.



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21 - Ans: D. See solution 803 at
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26 - Ans: D. See solution 74 at
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27 - Ans: A. See solution 952 at
What do not travel at the speed of light in a vacuum?



29 - Ans: C. See solution 526 at
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36 - Ans: C. See solution 1110 at
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37 - Ans: B. See solution 506 at
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• 9702 June 2013 Paper 41 & 43 Worked Solution | A-Level Physics

Question 2 - See solution 384 at
Two cylinders A and B are connected by a tube of negligible volume, as shown in Fig. 2.1.
Initially, tap T is closed. The cylinders contain an ideal gas at different pressures.



Question 4 - See solution 237 at
A charged particle is accelerated from rest in a vacuum through a potential difference V. Show that the final speed v of the particle is given by the expression



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Question 7 - See solution 360 at
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Question 11 - See solution 651 at
A radio station emits an amplitude-modulated wave for the transmission of music. 
State what is meant by an amplitude-modulated (AM) wave.

• 9702 November 2015 Paper 41 & 42 Worked Solution | A-Level Physics

Question 1
A satellite of mass mS is in a circular orbit of radius x about the Earth. The Earth may be considered to be an isolated uniform sphere with its mass M concentrated at its centre.



Question 3
(a) State an expression, in terms of work done and heating, that is used to calculate the increase in internal energy of a system.




Question 6
A particle has mass m, charge +q and speed v. State the magnitude and direction of the force




Question 9
A battery of e.m.f. 6.0 V and negligible internal resistance is connected to three resistors, each of resistance 2.0 kΩ, and a thermistor, as shown in Fig. 9.1.

Question 11

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• 9702 June 2016 Paper 42 Worked Solution | A-Level Physics

Question 1
A binary star consists of two stars A and B that orbit one another, as illustrated in Fig. 1.1.



Question 2
A container has a volume of 1.8 × 104 cm3.  The ideal gas in the container has a pressure of 2.0 × 107 Pa at a temperature of 17 °C.



Question 3
Suggest suitable types of thermometer, one in each case, to measure



Question 4
A metal block hangs vertically from one end of a spring. The other end of the spring is tied to a thread that passes over a pulley and is attached to a vibrator, as shown in Fig. 4.1.



Question 6
By reference to electric field lines, explain why, for points outside an isolated spherical conductor, the charge on the sphere may be considered to act as a point charge at its centre.



Question 7
State two uses of capacitors in electrical circuits, other than for the smoothing of direct current.



Question 8
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Question 10
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Question 11
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• 9702 November 2018 Paper 13 Worked Solution | A-Level Physics

1 C                  11 A                21 D                31 D

2 C                  12 B                22 B                32 A

3 C                  13 D                23 B                33 B

4 B                  14 D                24 D                34 C

5 B                  15 D                25 B                35 A

6 A                  16 B                26 D                36 D

7 B                  17 C                27 C                37 C

8 A                  18 C                28 C                38 C

9 A                  19 D                29 B                39 A

10 C                20 B                30 B                40 A

19 - Ans: D.
In an experiment to measure the Young modulus of a metal, a wire of the metal of diameter 0.25 mm is clamped, as shown.



37 - Ans: C.
In the circuit shown, the ammeter reading is zero. What is the resistance of resistor R?

• 9702 June 2010 Paper 41 Worked Solution | A-Level Physics

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Question 5 - See solution 590 at
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Question 9
The circuit diagram of Fig. 9.1 is an amplifier circuit incorporating an operational amplifier (op-amp).