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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 (pdf)

- What is a reasonable estimate of the kinetic energy of an Olympic athlete sprinting in a 100 m race?
- What is a unit of momentum?
- What is the horizontal component of the force shown?
- The diagram shows two readings on a micrometer.

By how much did the current really increase between taking the two readings? - The diameter of a circular disc is measured as (7.0 0.1) mm.

What is the area of the disc and the absolute uncertainty in the area? - The diagram shows a velocity–time graph for a car.
- A steel ball is dropped from rest from a height h above the ground. The ball hits the ground after
a time t.

This is repeated for a number of different heights.

The graph shows the variation of h with t^{2}for the ball.

The gradient of the graph is G.

Which expression gives the acceleration of the ball?

- Two masses, M and m, are connected by an inextensible string which passes over a frictionless
pulley. Mass M rests on a frictionless slope, as shown.

The slope is at an angle to the horizontal.

The two masses are initially held stationary and then released. Mass M accelerates down the slope.

Which expression must be correct? - The weights and masses of four different objects on the surfaces of four different planets are
shown.

Which planet has the lowest value of acceleration of free fall at its surface? - A rock in deep space is travelling towards a distant star and collides with a stationary spacecraft.

What is not a possible outcome of the collision? - A steel ball is falling at a constant (terminal) speed in still air. The forces acting on the ball are
upthrust, viscous drag and weight.

What is the order of increasing magnitude of these three forces? - What is a couple?
- Four coplanar forces act on a rigid rod, as shown. The rod is hinged at P.

Which force produces the greatest moment about point P? - A book of weight W has a rectangular shape and is of uniform thickness. The book is held in a vertical plane so that the longer sides of the book are vertical, as shown.
- The derivation of the pressure equation p = gh uses a number of relationships between
quantities.

Which relationship is not used in the derivation of this equation? - A spring is initially neither compressed nor extended.

A force can be applied to this spring so that it is either compressed to a shorter length or extended to a longer length.

What is the change in the elastic potential energy in the spring when it is extended and when it is compressed? - A sample of gas is sealed in a cylinder by a piston. The frictionless piston is free to move, so that
the pressure of the gas remains constant at 1.80 10
^{5}Pa. - A car of mass 500 kg is at rest at point X on a slope, as shown.

The car’s brakes are released and the car rolls down the slope with its engine switched off. At point Y the car has moved through a vertical height of 30 m and has a speed of 11 ms^{–1}. - Which expression cannot be used to calculate power?
- The stress in a material is given by the equation shown.
- What is an example of plastic deformation?

A A rubber ball is momentarily compressed every time it hits the ground.

B A spoon stirring some coffee in a ceramic mug hits its surface and makes a clinking sound.

C A toolbox is left on a horizontal plank. When the toolbox is removed, the plank is no longer straight.

D The spring in some bathroom weighing scales is compressed by a person standing on the scales. - A transverse progressive wave of wavelength is set up on a stretched string. The graph shows the variation of displacement y with distance x at a particular instant of time.
- The graph shows the variation with time of the displacement of an air particle as a progressive
sound wave passes through the air. The speed of sound in air is 330 ms
^{–1}. - A microphone is connected to a cathode-ray oscilloscope (CRO). A sound wave of constant frequency is detected by the microphone. The screen of the CRO is shown.
- A train’s whistle is emitting sound of frequency 500 Hz as the train moves with a speed of 20 m s–1 along a straight track. The train moves directly towards a stationary observer standing next to the track and then passes the observer.
- Gamma-rays, microwaves, visible light and X-rays are four regions of the electromagnetic spectrum. Which list shows these four regions in order of increasing wavelength?
- To produce a stationary wave, two waves must travel in opposite directions through the same space. Which statement about the properties of the two waves must also be correct?
- The speed of sound in air is 330 ms
^{–1}. Which size of architectural features in a large concert hall would best diffract sound waves of frequency 0.44 kHz? - A double-slit interference pattern using red light of wavelength 7.0 10
^{–7}m has a fringe spacing of 3.5 mm. Which change would cause the distance between the bright lines on the screen to be reduced? - A beam of light of a single wavelength is incident normally on a diffraction grating.

The angle of diffraction is measured for each order of diffraction n. The distance between adjacent slits in the diffraction grating is d.

A graph is plotted to determine the wavelength of the light.

Which graph should be plotted and how is the wavelength determined from the graph? - A particle has a charge of +2.0 mC and is in a vertical uniform electric field. An electric force of
1.0 10–2N acts upwards on the particle.

What is the electric field strength? - The diagram shows two parallel metal plates connected to a d.c. power supply through a resistor.
- A wire has a length of 12 cm and contains a total of 5.1 10
^{22}free electrons - A battery is marked 9.0V.

What does this mean? - The diagram shows a circuit containing two batteries connected together.
- The circuit shown includes a cell of constant internal resistance and an external resistor R.
- A battery of electromotive force (e.m.f.) E and negligible internal resistance is connected to four resistors of resistances R1, R2, R3 and R4.
- In the circuit shown, a potentiometer of total resistance 120 is connected in parallel with a resistor of resistance 150 and a resistor of resistance R.
- A beam of -particles is incident on a thin gold foil. One -particle collides head-on with a gold
nucleus and is deflected back along its original path.

Which statement could explain why the recoil speed of the gold nucleus is small compared with the recoil speed of the -particle? - A hadron is composed of three quarks. The hadron has a charge.

What is a possible quark composition of the hadron?

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