A Level Physics 9702 Paper 22, Oct/Nov 2025

The scientists take measurements of several physical quantities at each location. Complete Table 1.1 by stating the SI base unit for each quantity and identifying with a tick (✓) whether each quantity is a scalar or a vector. Use the space for any working. Table 1.1

At one location, the density of the air is $1.1\text{ kg}{\text{ m}}^{-3}$. A spherical weather balloon is filled with a gas and released from rest. The balloon has radius $0.90\text{ m}$. Calculate the upthrust acting on the balloon when it is released. upthrust = ...................................................... N

Explain why an upthrust acts on the balloon.

The balloon has weight $19\text{ N}$. Calculate the magnitude of the initial acceleration of the balloon. acceleration = ................................................ ${\text{ms}}^{-2}$

A quantity $c$ relating to the motion of the balloon is calculated from three measured quantities $k$, $F$ and $v$ using the formula $$c=\frac{2kF}{v^2}\mathrm{.}$$ The percentage uncertainties in the measured quantities are given in Table 1.2. Table 1.2

The calculated value of $c$ is $1.8$. Determine the absolute uncertainty in $c$. absolute uncertainty = .........................................................

Thruster A is activated, producing a force of $60\text{ N}$ upwards on the spacecraft. Thruster C is also activated, producing a force of $220\text{ N}$ in the leftwards direction on the spacecraft. Calculate the resultant moment due to these forces about the centre of gravity. resultant moment = ...................................................Nm

State and explain whether the forces from A and C are a couple.

Thrusters A and C are now switched off and the spacecraft is stationary. Thruster B is activated at time $t_1$, producing a constant force on the spacecraft until the fuel runs out at time $t_2$. As the fuel is used, the total mass of the spacecraft decreases. On Fig. 2.2, sketch the variation of speed of the spacecraft with time from $t_1$ to $t_2$.

The spacecraft now splits apart into a carrier and a payload as shown in Fig. 2.3. During the split, an average force of $5500\text{ N}$ acts on the payload for a time of $0.36\text{ s}$. The velocity of the payload increases by $8.5{\text{ ms}}^{-1}$ in the upwards direction. The combined mass of the carrier and payload is $2.5\times {10}^3\text{ kg}$. State the principle of conservation of momentum.

Show that the mass of the payload is $230\text{ kg}$.

Calculate the magnitude of the change in velocity of the carrier. change in velocity = ................................................ ${\text{ms}}^{-1}$

On Fig. 3.2, draw labelled arrows to show the directions of the forces acting on the pulley.

The force $F$ is $110\text{ N}$. Determine $T$. $T$ = ...................................................... N

Calculate the extension of the spring. extension = ......................................................m

A second identical spring with the same spring constant of $250{\text{ Nm}}^{-1}$ is now also connected to the pulley, as shown in Fig. 3.3. The tension in the cable is kept the same. The pulley is again in equilibrium. Determine the extension of the springs. extension = ..................................................... m

The elastic potential energy stored in the spring in Fig. 3.1 is $E_1$. The total elastic potential energy stored in the two springs in Fig. 3.3 is $E_2$. Calculate the ratio $\frac{E_1}{E_2}$. ratio = .........................................................

Explain how the pattern of bright and dark fringes is formed.

Calculate the frequency of the light emitted by the laser. frequency = .................................................... Hz

The double slit is removed. A second laser is placed beside the first laser. The second laser produces visible light of a different frequency from that of the first laser. The beams of light from the two lasers overlap on the screen. Explain why a steady pattern of bright and dark fringes is not formed on the screen.

State Kirchhoff’s first law.

The intensity of light incident on Z is $130{\text{ Wm}}^{-2}$. The current in the battery is $38\text{ mA}$. Show that the terminal potential difference of the battery is $4.8\text{ V}$.

Calculate the current $I_2$ in Y. $I_2$ = ...................................................... A

Calculate the power dissipated in Y. power = ..................................................... W

The intensity of the light incident on Z decreases. State and explain the effect on the terminal potential difference of the battery.

State what is meant by a fundamental particle.

Particle Q is a meson with a charge of 0. Determine a possible quark composition for Q.

Particle Q has a mass of $0.67\text{ u}$ and a kinetic energy of $2.1\times {10}^{-16}\text{ J}$. Calculate the speed of particle Q. speed = ................................................ ${\text{ms}}^{-1}$

Radium-228 (${}_{88}^{228}\text{Ra}$) is a radioactive nuclide. State the number of electrons in a neutral atom of radium-228. number of electrons = .........................................................

A nucleus of radium-228 undergoes a series of decays to form nucleus X. During the process, 5 $\alpha$-particles and 4 ${\beta }^{-}$ particles are emitted. Determine the number of protons and the number of neutrons in nucleus X. number of protons = ............................................................... number of neutrons = ...............................................................