A Level Physics 9702 Paper 23, May/June 2026

Define momentum.

A ball X of mass $0.15\text{ kg}$ moves along a horizontal frictionless surface. The ball collides elastically with ball Y that is initially stationary. Balls X and Y have equal diameters but different masses. Figure 1.1 shows the variation with time of the velocity of ball X before, during and after the collision. Determine the magnitude of the acceleration of ball X during the collision. acceleration = ................................................ ${\text{ms}}^{-2}$

Determine the magnitude of the change in momentum of ball X due to the collision. change in momentum = ............................................ $\text{kg}{\text{ms}}^{-1}$

Determine the total distance travelled by ball X during the collision. distance = ......................................................$\text{m}$

By considering relative speeds, explain why the velocity of ball Y after the collision must be $+0.80{\text{ ms}}^{-1}$.

On Figure 1.1, sketch the variation of the velocity of ball Y with time between $\text{time}=0$ and $\text{time}=0.20\text{ s}$.

Calculate the mass of ball Y. mass = ..................................................... $\text{kg}$

Define the Young modulus of a material.

A long, thin thread of high-density polythene has a uniform cross-section. The thread is suspended from one end so that it hangs vertically. The thread has a mass of $0.018\text{ kg}$ and a cross-sectional area of $2.6\times {10}^{-6}{\text{ m}}^2$. High-density polythene has a density of $960\text{ kg}{\text{m}}^{-3}$ and a Young modulus of $8.0\times {10}^8\text{ Pa}$. Show that the length of the thread is $7.2\text{ m}$.

Show that the stress at the top of the thread due to its own weight is $6.8\times {10}^4\text{ Pa}$.

Figure 2.1 shows the variation with distance from the top of the thread of the stress in the thread due to its own weight. Suggest an explanation for the fact that the variation shown in Figure 2.1 is linear.

The thread in 2(b) is now laid horizontally on a frictionless bench. A tensile force is applied to the ends of the thread so that there is a uniform stress throughout the thread of $6.8\times {10}^4\text{ Pa}$. Calculate the extension of the thread. extension = ......................................................$\text{m}$

Calculate the elastic potential energy of the thread. elastic potential energy = ....................................................... $\text{J}$

Suggest, with a reason, whether the total extension of the vertically suspended thread in 2(b) is less than, equal to or greater than the answer in 2(c)(i).

State the principle of superposition.

Parallel rays of coherent light of wavelength $560\text{ nm}$ are incident normally in free space on two narrow slits as shown in Figure 3.1. Light passing through the double slit reaches a screen that is parallel to the plane of the slits. The distance between the centres of the slits is $1.4\times {10}^{-5}\text{ m}$. The distance between the slits and the screen is $0.43\text{ m}$. State what is meant by coherent.

State what happens to the light at the point where it passes through the slits.

At point X on the screen, there is a central bright fringe. Explain how this bright fringe is formed.

At point Y on the screen, the dark fringe closest to point X is formed. Calculate the distance XY. distance = ......................................................$\text{m}$

On the screen in Figure 3.1: draw a cross (×) labelled with the letter B at the position of another bright fringe

draw a cross (×) labelled with the letter D at the position of another dark fringe.

Calculate the frequency of the light in 3(b). frequency = .................................................... $\text{Hz}$

Draw a circuit diagram to show this arrangement.

The cell has an electromotive force (e.m.f.) of $4.90\text{ V}$. At a particular light intensity, the LDR has a resistance of $230\mathrm{\Omega }$ and a potential difference (p.d.) across it of $4.78\text{ V}$. Identify one possible source of systematic error in measuring the p.d. across the LDR using a digital voltmeter.

Calculate the power dissipated in the LDR. power = ..................................................... $\text{W}$

Determine the internal resistance of the cell. internal resistance = ...................................................... $\mathrm{\Omega }$

The intensity of the light illuminating the LDR is gradually decreased. By placing one tick (✓) in each row, complete Table 4.1 to show what happens to the quantities indicated as the light intensity decreases. Table 4.1

State what is meant by a meson.

The elementary charge is $e$. Explain, in terms of quark composition, how a baryon may have an overall charge of: • $-1e$ .................................................................................................................................... ........................................................................................................................................... • $+2e$ .................................................................................................................................... ...........................................................................................................................................

The nuclide ${}_8^{18}\text{X}$ undergoes ${\beta }^{+}$ decay to produce nuclide ${}_Q^P\text{Y}$ and one other particle Z, as shown in the equation $${}_8^{18}\text{X}\to {}_Q^P\text{Y}+{}_S^R{\beta }^{+}+{}_0^0\text{Z}$$ State the values of $P$, $Q$, $R$ and $S$. $P$ = ............................................................... $Q$ = ............................................................... $R$ = ............................................................... $S$ = ...............................................................

State the name of particle Z.

State the net change in quark composition as nuclide X turns into nuclide Y.

Explain why the emission of particle Z results in the ${\beta }^{+}$ particles from the decays of different nuclei of ${}_8^{18}\text{X}$ having a continuous range of kinetic energies.