The diagram shows the waveform of a signal displayed on a cathode-ray oscilloscope.

Question 15

The diagram shows the waveform of a signal displayed on a cathode-ray oscilloscope.

The time-base is set at 5.0 ms per division.

The Y-gain is set at 5.0 mV per division.

What are the amplitude and the frequency of the signal?

amplitude / mV            frequency / Hz

A                     10                                50

B                     10                                100

C                     20                                50

D                     20                                100

Reference: Past Exam Paper – November 2018 Paper 11 Q23

Solution:

Answer: A.

The amplitude is measured (vertically) starting from the central line to the peak.

Y-gain = 5.0 mV per div

Amplitude = 2 div = 2 × 5.0 = 10 mV

The period is measured horizontally. One complete wave occupies 4 div.

Time-base setting = 5.0 ms per div

Period T = 4 div = 4 × 5.0 = 20 ms = 20×10^-3 s

 

Frequency = 1 / T = 1 / (20×10^-3) = 50 Hz

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.



10 - Ans: C. See solution 1061 at
A golf ball is hit with the same force and direction on the Earth and on the Moon. Which diagram best represents the shapes of the paths taken by the golf ball?


11 - Ans: C. See solution 177 at
An object travelling with velocity v strikes a wall and rebounds as shown. Which property of the object is not conserved?




13 - Ans: A. See solution 66 at
A mass of 2.0 kg rests on a frictionless surface. It is attached to a 1.0 kg mass by a light, thin string which passes over a frictionless pulley.



15 - Ans: B. See solution 775 at
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18 - Ans: A. See solution 67 at
The kinetic energy of a particle is increased by a factor of 4.  By what factor does its speed increase?



21 - Ans: D. See solution 803 at
Water from a reservoir is fed to the turbine of a hydroelectric system at a rate of 500 kg s-1. The reservoir is 300 m above the level of the turbine.



23 - Ans: A. See solution 1113 at
Three springs are arranged vertically as shown. Springs P and Q are identical and have spring constant k. Spring R has spring constant 3k.


25 - Ans: B. See solution 70 at
A steel wire and a brass wire are joined end to end and are hung vertically with the steel wire attached to a point on the ceiling.


26 - Ans: D. See solution 74 at
The diagram shows a graph of displacement against time for a sound wave.


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
Monochromatic light is directed at a diffraction grating as shown. Which diagram shows all the possible directions of the light, after passing through the grating, that give maximum intensity?



36 - Ans: C. See solution 1110 at
A network of electrical components is connected across a battery of negligible internal resistance, as shown.


37 - Ans: B. See solution 506 at
The diagram shows a potentiometer circuit. The contact T is placed on the wire and moved along the wire until the galvanometer reading is zero. The length XT is then noted.