A-LevelPhysicsParticle physics9702/21 · Oct/Nov 2020 · Q87 Marks

State a similarity and a difference between a down quark and a down antiquark.

(a)State a similarity and a difference between a down quark and a down antiquark.[2]
(b)(i)For a nucleus of aluminium-25 (²⁵₁₃Al): state the number of protons and the number of neutrons[1]
(b)(ii)show that the charge is 2.1 × 10⁻¹⁸ C.[1]
(c)The nucleus in (b) is moved along a straight line from point A to point B in a uniform horizontal electric field in a vacuum, as shown in Fig. 8.1. [Figure 8.1] The electric field strength is 11 kV m⁻¹. Calculate the work done to move the charge from A to B.[3]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[B1] similarity: same/equal mass or same/equal (magnitude of) charge or both fundamental (particles)
[B1] difference: opposite (sign of) charge or one is matter and the other is antimatter
[A1] number of protons = 13 and number of neutrons = 12
[A1] (charge =) 13 × 1.60 × 10⁻¹⁹ (C) = 2.1 × 10⁻¹⁸ (C)
[C1] force = 11 x 10³ x 2.1 × 10⁻¹⁸
[C1] work done = 11 x 10³ x 2.1 × 10⁻¹⁸ × 0.04
[A1] = 9.2 × 10⁻¹⁶ J

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