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Various options are provided as possible answers to the following questions - NSC Physical Sciences - Question 1 - 2018 - Paper 1
Question 1
Various options are provided as possible answers to the following questions. Choose the answer and write down only the letter (A–D) next to the question numbers (1.1... show full transcript
Worked Solution & Example Answer:Various options are provided as possible answers to the following questions - NSC Physical Sciences - Question 1 - 2018 - Paper 1
Step 1
1.1 The net (resultant) force acting on an object is equal to the ... of the object in the direction of the net force.
Answer
The net (resultant) force acting on an object is equal to the rate of change of momentum of the object in the direction of the net force. Thus, the correct answer is C. rate of change of momentum.
Step 2
1.3 At which ONE of the positions indicated on the diagram will the magnitude of the momentum of the stone be the GREATEST? Ignore air resistance.
Answer
The magnitude of momentum is given by the product of mass and velocity. At the highest point (position II), the velocity is momentarily zero, so momentum is zero there. The momentum is greatest at position I, where the stone is moving at its maximum speed. Therefore, the answer is I.
Step 3
1.6 Which ONE of the following is NOT an application of the Doppler effect?
Answer
The Doppler effect applies to situations where there is a change in frequency or wavelength due to the relative motion of a source and an observer. Among the options, detecting the heartbeat of a foetus using ultrasound does not rely on the Doppler effect but rather the use of sound waves for imaging. Thus, the correct answer is C. Detecting the heartbeat of a foetus using ultrasound.
Step 4
1.7 The magnitude of the electrostatic force which the spheres now exert on each other, in terms of F, is:
Answer
When the identical spheres with charges -q and +3q touch, they will share their charges and each will end up with a charge of +q. The force acting between two charges is given by Coulomb’s law, which states that the force F between two point charges is proportional to the product of the absolute values of the charges divided by the square of the distance between their centers. Thus, the new force is:
Therefore, the answer is B. 2/3 F.
Step 5
1.8 Switch S is now closed. How do the readings on the ammeter and voltmeter change?
Answer
When the switch is closed, the current will increase as the circuit is complete. The ammeter will register an increase in current, while the voltmeter will show a decrease because of the internal resistance of the battery affecting the voltage. Therefore, the correct answer is B. Increases (Ammeter), Decreases (Voltmeter).
Step 6
1.9 In which ONE of the combinations below is CORRECT?
Answer
All three factors listed affect the magnitude of the current induced in an AC generator: the number of turns of the coil, the strength of the magnetic field, and the speed of rotation. Hence, the correct answer is D. (i), (ii), and (iii).
Step 7
1.10 Which ONE of the following represents the gradient of the graph?
Answer
In the context of the photoelectric effect, the gradient of the plot of energy against the reciprocal of wavelength corresponds to Planck's constant multiplied by the speed of light (hc). Therefore, the correct answer is A. hc.