Physics: Standard Level
Fields — Theme D
- 1.
State Newton's law of gravitation, and use it to explain why gravitational force decreases with the square of separation.
[3 marks] · no calculator - 2.
Marking analysis: A learner attempts the following task: “State Newton's law of gravitation, and use it to explain why gravitational force decreases with the square of separation.” Their response addresses only this point: “States F = Gm₁m₂/r², where G is the gravitational constant.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 3.
Calculate the gravitational field strength at the surface of a planet of mass 4.0 × 10²⁴ kg and radius 5.0 × 10⁶ m. Use G = 6.67 × 10⁻¹¹ N m² kg⁻².
[3 marks] - 4.
Marking analysis: A learner attempts the following task: “Calculate the gravitational field strength at the surface of a planet of mass 4.0 × 10²⁴ kg and radius 5.0 × 10⁶ m. Use G = 6.67 × 10⁻¹¹ N m² kg⁻².” Their response addresses only this point: “Uses g = GM/r².” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 5.
Define electric field strength, and state its direction relative to a positive test charge.
[2 marks] · no calculator - 6.
Marking analysis: A learner attempts the following task: “Define electric field strength, and state its direction relative to a positive test charge.” Their response addresses only this point: “Defines electric field strength as the electric force per unit positive charge experienced at a point.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 7.
Two point charges of +3.0 μC and −3.0 μC are separated by 0.20 m. Calculate the magnitude of the electric force between them. Use k = 8.99 × 10⁹ N m² C⁻².
[3 marks] - 8.
Marking analysis: A learner attempts the following task: “Two point charges of +3.0 μC and −3.0 μC are separated by 0.20 m. Calculate the magnitude of the electric force between them. Use k = 8.99 × 10⁹ N m² C⁻².” Their response addresses only this point: “Uses Coulomb's law F = kq₁q₂/r².” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 9.
Explain why a charged particle moving parallel to a uniform magnetic field experiences no magnetic force, while one moving perpendicular to the field does.
[3 marks] · no calculator - 10.
Marking analysis: A learner attempts the following task: “Explain why a charged particle moving parallel to a uniform magnetic field experiences no magnetic force, while one moving perpendicular to the field does.” Their response addresses only this point: “States that the magnetic force on a moving charge is given by F = qvB sinθ, where θ is the angle between velocity and field.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 11.
A charged particle moves in a circular path perpendicular to a uniform magnetic field. State the direction of the magnetic force at any instant, relative to the particle's velocity.
[2 marks] · no calculator - 12.
Marking analysis: A learner attempts the following task: “A charged particle moves in a circular path perpendicular to a uniform magnetic field. State the direction of the magnetic force at any instant, relative to the particle's velocity.” Their response addresses only this point: “States that the magnetic force is always perpendicular to the particle's velocity.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 13.
Define gravitational potential energy in a radial field, and explain why it is defined to be negative for a mass at a finite distance from another mass.
[3 marks] · no calculator - 14.
Marking analysis: A learner attempts the following task: “Define gravitational potential energy in a radial field, and explain why it is defined to be negative for a mass at a finite distance from another mass.” Their response addresses only this point: “Defines gravitational potential energy as the work done to bring a mass from infinity to a point in the gravitational field.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 15.
A satellite orbits Earth in a circular orbit of radius r. Show that its orbital period T satisfies T² ∝ r³, using Newton's law of gravitation and the centripetal force equation.
[4 marks] · no calculator - 16.
Marking analysis: A learner attempts the following task: “A satellite orbits Earth in a circular orbit of radius r. Show that its orbital period T satisfies T² ∝ r³, using Newton's law of gravitation and the centripetal force equation.” Their response addresses only this point: “Equates gravitational force to the required centripetal force: GMm/r² = mv²/r (or equivalently mω²r).” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] · no calculator - 17.
A parallel plate capacitor has a uniform electric field of 2000 V m⁻¹ between its plates, which are 0.050 m apart. Calculate the potential difference between the plates.
[3 marks] - 18.
Marking analysis: A learner attempts the following task: “A parallel plate capacitor has a uniform electric field of 2000 V m⁻¹ between its plates, which are 0.050 m apart. Calculate the potential difference between the plates.” Their response addresses only this point: “Uses E = V/d for a uniform field between parallel plates.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 19.
Compare the direction of the gravitational force between two masses with the direction of the electric force between two like (same-sign) charges.
[2 marks] · no calculator - 20.
Marking analysis: A learner attempts the following task: “Compare the direction of the gravitational force between two masses with the direction of the electric force between two like (same-sign) charges.” Their response addresses only this point: “States that the gravitational force between two masses is always attractive.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 21.
Calculate the electric potential at a point 0.30 m from a point charge of +5.0 μC. Use k = 8.99 × 10⁹ N m² C⁻².
[3 marks] - 22.
Marking analysis: A learner attempts the following task: “Calculate the electric potential at a point 0.30 m from a point charge of +5.0 μC. Use k = 8.99 × 10⁹ N m² C⁻².” Their response addresses only this point: “Uses V = kQ/r.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 23.
Define capacitance, and calculate the capacitance of a capacitor that stores a charge of 6.0 × 10⁻⁴ C when the potential difference across it is 12 V.
[3 marks] - 24.
Marking analysis: A learner attempts the following task: “Define capacitance, and calculate the capacitance of a capacitor that stores a charge of 6.0 × 10⁻⁴ C when the potential difference across it is 12 V.” Their response addresses only this point: “Defines capacitance as the charge stored per unit potential difference: C = Q/V.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 25.
Calculate the energy stored in a 5.0 × 10⁻⁵ F capacitor when it is charged to a potential difference of 12 V.
[3 marks] - 26.
Marking analysis: A learner attempts the following task: “Calculate the energy stored in a 5.0 × 10⁻⁵ F capacitor when it is charged to a potential difference of 12 V.” Their response addresses only this point: “Uses energy = ½CV².” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 27.
Define gravitational potential at a point, and calculate the gravitational potential at the surface of a planet of mass 6.0 × 10²⁴ kg and radius 6.4 × 10⁶ m. Use G = 6.67 × 10⁻¹¹ N m² kg⁻².
[4 marks] - 28.
Marking analysis: A learner attempts the following task: “Define gravitational potential at a point, and calculate the gravitational potential at the surface of a planet of mass 6.0 × 10²⁴ kg and radius 6.4 × 10⁶ m. Use G = 6.67 × 10⁻¹¹ N m² kg⁻².” Their response addresses only this point: “Defines gravitational potential as the work done per unit mass to bring a small test mass from infinity to that point.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 29.
A straight wire of length 0.50 m carries a current of 4.0 A perpendicular to a uniform magnetic field of flux density 0.20 T. Calculate the magnetic force on the wire.
[3 marks] - 30.
Marking analysis: A learner attempts the following task: “A straight wire of length 0.50 m carries a current of 4.0 A perpendicular to a uniform magnetic field of flux density 0.20 T. Calculate the magnetic force on the wire.” Their response addresses only this point: “Uses F = BIL for a wire perpendicular to the field.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks]