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This page covers Questions and Worked Solutions for Physics 9702 Paper 13 October 2021, 9702/13.

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2021 Physics 9702 Paper 13 Oct/Nov (pdf)

- A paperback book contains 210 sheets of paper (pages). Its thickness is measured with a ruler,
as shown.

What is the average thickness of one sheet of the paper in the book? - What is the unit of resistance when expressed in SI base units?
- Which list consists only of scalar quantities?
- The output of a signal generator is connected to a cathode-ray oscilloscope (CRO). A trace is
shown on the screen.

The time-base of the CRO is set at 2.00 ms cm^{–1}.

What is the frequency of the signal? - After measuring the width of a shelf to be 305 mm, it is found that the graduations on the ruler
used are 1.0% further apart than they should be.

Which type of measurement error is this and what is the true width of the shelf? - The graph shows the variation with time of the acceleration of a car.
- A stone is thrown horizontally off a cliff and then lands in the sea. Air resistance is negligible.

- Water is pumped through a hose-pipe at a rate of 90 kg per minute. Water emerges horizontally
from the hose-pipe with a speed of 20 m s
^{–1}.

What is the minimum force required from a person holding the hose-pipe to prevent it moving backwards? - A skydiver leaves a stationary balloon and falls vertically through a long distance.

Which graph best represents the variation of the acceleration a of the skydiver with the distance s travelled as she falls through the air? - The diagram shows two spheres approaching each other head-on. Each sphere has speed u.

One sphere has mass 2m and the other has mass m. - A spherical object falls through water at a constant speed. Three forces act on the object.

Which diagram, showing these three forces to scale, is correct? - Two forces act as a couple.

Which statement about the two forces must not be correct? - A sign outside a shop is suspended from a rusty horizontal hinge at its top end. The sign hangs in equilibrium at an angle of 25° to the vertical, as shown.
- A uniform rod of length 200 cm is freely pivoted at point P. The rod is held horizontally in equilibrium by a 60 N weight that is attached to the rod by a string passing over a frictionless pulley.
- The diagram shows two blocks X and Y.
- A gas is contained inside a syringe, as shown.
- A mechanical device does useful work at rate X and wastes energy at rate Y.

Which expression gives the efficiency of this device? - Car P has kinetic energy 240 kJ.

Car Q has half the mass and twice the speed of car P.

What is the kinetic energy of car Q? - A water pump is driven by an engine. The pump raises a volume of 0.50 m
^{3}of water in 1.0 minute

from a depth of 30 m. The pump has an efficiency of 70%. - Which spring combination has an overall spring constant of 8.0 N m
^{–1}? - A metal wire is stretched to breaking point and the force–extension graph is plotted.

Which graph is correctly labelled with the elastic region, the plastic region and the area representing the work done to stretch the wire until it breaks? - A longitudinal wave travels through a long spring. The spring is shown at one instant.

What is the wavelength of the wave? - Which statement about waves is correct?
- A stationary sound wave is formed in a pipe that is closed at one end and open at the other end.

The wave has two antinodes. One of these antinodes is at the open end of the pipe. - A train travels at constant speed along a straight track. The train’s horn emits sound of frequency
500Hz.

A person standing by the side of the track hears sound of frequency 450Hz. - A smooth surface has bumps on the surface that are smaller than the wavelength of visible light.

What is the approximate maximum size of the largest bumps on the surface? - Two progressive waves travel in opposite directions and form a stationary wave. The graph shows the variation with distance x of the displacement of the stationary wave and of one of the two progressive waves at the same instant in time.
- Which diagram shows the diffraction of water waves in a ripple tank?
- Interference fringes are produced on a screen by double-slit interference using light of wavelength 600 nm. The fringe separation is 4.0 mm and the separation of the slits is 0.60 mm. What is the distance between the double slit and the screen?
- A ray of green light is incident normally on a diffraction grating. Several bright spots are produced on a screen on the other side of the grating, as shown.
- Two parallel metal plates are at electric potentials of +800V and +1300V.

Which diagram best represents the electric field between the metal plates? - An electron is in a uniform electric field of field strength 1500V m
^{–1}.

What is the acceleration of the electron due to the electric field? - A lightning strike transfers 1 x 10
^{20}electrons past a point in a time of 30 µs.

What is the average current during the lightning strike? - A cell has an electromotive force (e.m.f.) of 6V and internal resistance R. An external resistor, also of resistance R, is connected across this cell, as shown.
- A wire of uniform cross-section has resistance R.

A second wire is made of the same material but is twice as long and has twice the diameter of the first wire.

What is the resistance of the second wire? - The diagram shows two resistor networks.
- The circuit shown contains three cells of electromotive forces 3.0V, 2.0V and 4.0V, in series with a resistor of resistance 5.0Ω. The cells have negligible internal resistance
- When α-particles are fired at a thin metal foil, most of the particles pass straight through but a few
are deflected by a large angle.

Which change would increase the proportion of α-particles deflected by a large angle? - A nucleus of neptunium-236 contains 93 protons and 143 neutrons. This nucleus decays with the
emission of an α-particle. The nucleus formed then emits a α–
particle.

Which diagram shows the changes in the number P of protons and the number N of neutrons in these nuclei? - Which combination of quarks could not be the quark composition of the hadron shown?

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