(a) Use the definition of work done to show that the SI base units of energy are kg m² s^-2.

[2]

(b) Define potential difference.

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[1]

(c) Determine the SI base units of resistance. Show your working.

units ............................................................... [3]

A stone is thrown vertically upwards. The variation with time $t$ of the displacement $s$ of the stone is shown in Fig. 2.1.

(a) Use Fig. 2.1 to describe, without calculation, the speed of the stone from $t = 0$ to $t = 3.0s$. [2]

(b) Assume air resistance is negligible and therefore the stone has constant acceleration.

Calculate, for the stone,

(i) the speed at 3.0 s, [3]

(ii) the distance travelled from $t = 0$ to $t = 3.0, ext{s}$,  [3]

(iii) the displacement from $t = 0$ to $t = 3.0, ext{s}$. [2]

(c) On Fig. 2.2, draw the variation with time $t$ of the velocity $v$ of the stone from $t = 0$ to $t = 3.0, ext{s}$. [3]

A rod PQ is attached at P to a vertical wall, as shown in figure 1.

The length of the rod is 1.60 m. The weight $W$ of the rod acts 0.64 m from P. The rod is kept horizontal and in equilibrium by a wire attached to Q and to the wall at R. The wire provides a force $F$ on the rod of 44 N at 30° to the horizontal.

(a) Determine

(i) the vertical component of $F$,   [1]

(ii) the horizontal component of $F$.   [1]

(b) By taking moments about P, determine the weight $W$ of the rod.  [2]

(c) Explain why the wall must exert a force on the rod at P.  [1]

(d) On Figure 1, draw an arrow to represent the force acting on the rod at P. Label your arrow with the letter S. [1]

(a) A gas molecule has a mass of $6.64 \times 10^{-27} \text{ kg}$ and a speed of $1250 \text{ ms}^{-1}$. The molecule collides normally with a flat surface and rebounds with the same speed, as shown in Fig. 4.1.

Calculate the change in momentum of the molecule.     [2]

(b) (i) Use the kinetic model to explain the pressure exerted by gases.     [3]

(ii) Explain the effect of an increase in density, at constant temperature, on the pressure of a gas.   [1]

(a) On Fig. 5.1, sketch the temperature characteristic of a thermistor.
[Image: Fig. 5.1 graph with resistance vs. temperature/°C]

(b) A potential divider circuit is shown in Fig. 5.2.
[Image: Fig. 5.2 circuit diagram]
The battery of electromotive force (e.m.f.) 12 V and negligible internal resistance is connected in series with resistors X and Y and thermistor Z. The resistance of Y is 15 kΩ and the resistance of Z at a particular temperature is 3.0 kΩ. The potential difference (p.d.) across Y is 8.0 V.
(i) Explain why the power transformed in the battery equals the total power transformed in X, Y, and Z.
...
[1]
(ii) Calculate the current in the circuit.
current = ... A
[2]
(iii) Calculate the resistance of X.
resistance = ... Ω
[3]
(iv) The temperature of Z is increased. State and explain the effect on the potential difference across Z.
...
[2]

(a) State two differences between progressive waves and stationary waves. 

(b) A source S of microwaves is placed in front of a metal reflector R, as shown in Fig. 6.1. (2)

A microwave detector D is placed between R and S.

Describe

(i) how stationary waves are formed between R and S,  (3)

(ii) how D is used to show that stationary waves are formed between R and S,   (2)

(iii) how the wavelength of the microwaves may be determined using the apparatus in Fig. 6.1. (2)

(c) The wavelength of the microwaves in (b) is 2.8 cm. Calculate the frequency, in GHz, of the microwaves.   (3)

A uranium-235 nucleus absorbs a neutron and then splits into two nuclei. A possible nuclear reaction is given by $$^{235}_{92}U + ^{a}_{b}n \rightarrow ^{93}_{37}Rb + ^{c}_{d}X + 2^{a}_{b}n + \text{ energy.}$$

 
(a) State the constituent particles of the uranium-235 nucleus.

 
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(b) Complete Fig. 7.1 for this reaction.

 
(c) Suggest a possible form of energy released in this reaction.

 
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(d) Explain, using the law of mass-energy conservation, how energy is released in this reaction.

 
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