CIE iGCSE Co-Ordinated Science P1.2 Motion Exam Style Questions Paper 3
Question
Another student wears a white T-shirt in the Sun and does not become as hot.
Explain why.
Most-appropriate topic codes (Cambridge IGCSE Coordinated Sciences 0654):
• Topic P1.2 — Motion (Part (a)(i))
• Topic P1.6.4 — Power (Part (a)(ii))
• Topic P2.2.2 — Melting, boiling and evaporation (Part (b)(i))
• Topic P2.3.3 — Radiation (Part (b)(ii))
• Topic P6.2.1 — The Sun as a star (Part (b)(iii), (b)(iv))
▶️ Answer/Explanation
(a)(i) evidence of total time = 15 (s); v = s/t (in any form) OR (average speed =) 100/15; 6.7 (m/s)
Total time = 3.7 + 3.1 + 2.6 + 2.6 + 3.0 = 15.0 s. Average speed = 100/15 = 6.7 m/s.
(a)(ii) P = W/t (in any form) OR (work done =) 600 × 3.0; 1800; J
Work done = power × time = 600 × 3.0 = 1800 J. The unit for work is the joule (J).
(b)(i) evaporation
Sweating cools the body because the most energetic water particles evaporate from the skin surface, taking thermal energy with them and lowering the skin temperature.
(b)(ii) white absorbs less (thermal) radiation / white reflects more (thermal) radiation
White surfaces reflect most incident radiation, so less thermal energy is absorbed. Black surfaces absorb more radiation, leading to greater heating.
(b)(iii) helium or hydrogen
The Sun is composed mainly of hydrogen (about 75%) and helium (about 25%), with small amounts of other elements.
(b)(iv) infrared; (visible) light; ultraviolet
The Sun emits energy across the electromagnetic spectrum, but most is in the infrared, visible, and ultraviolet regions.
Question
Topic codes:
• Topic P1.2 — Motion (Part (a)(i) & (a)(ii))
• Topic P2.1.2 — Particle model (Part (b))
• Topic P1.5.2 — Turning effect of forces (Part (c))
• Topic P4.2.1 — Electrical charge (Part (d)(i), (d)(ii) & (d)(iii))
▶️ Answer/Explanation
(a)(i) Any time between t = 0 to t = 40 s
The car is accelerating when the speed is increasing. From the graph, the speed increases from 0 to 8 m/s during the first 40 seconds (the line slopes upwards). Any time within this interval shows acceleration.
(a)(ii) 560 m
Total distance travelled = area under the speed-time graph.
The graph forms a trapezium split into three sections:
- Triangle 1 (0 to 40 s): \(\frac{1}{2} \times 40 \times 8 = 160\) m
- Rectangle (40 to 80 s): \(40 \times 8 = 320\) m
- Triangle 2 (80 to 100 s): \(\frac{1}{2} \times 20 \times 8 = 80\) m
Total distance = 160 + 320 + 80 = 560 m
(b) Particles move faster / have greater kinetic energy / \(E_k\)
As temperature increases, the air particles gain kinetic energy. They move more rapidly, colliding with each other and the tyre walls more frequently and with greater force. This increased motion causes the pressure in the tyre to rise.
(c) Moment = 720 Ncm
Moment = force × perpendicular distance from the pivot.
Moment = 40 N × 18 cm = 720 Ncm
(Note: The perpendicular distance is measured from the pivot to the line of action of the force. Here it is given as 18 cm.)
(d)(i) Friction
As the car moves, friction between the car and the air, and between the tyres and the road, causes the transfer of electrostatic charges. This is similar to charging by friction where electrons are transferred from one surface to another.
(d)(ii) Electrons
The charged particles that move during the transfer of electrostatic charge are electrons. They are negatively charged and are transferred from one material to another during friction.
(d)(iii) \(-1\)
Electrons have a relative charge of \(-1\). This means they have a negative charge equal in magnitude to the positive charge of a proton (\(+1\)).