How do I approach this question? Our teacher never explained it in class!
Any question in physics will boil down to a simple conservation law, even at the relatively difficult A level exams.
Basically, in order to successfully solve this question, you need to identify 3 key things:
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Is there a net force acting on the object?
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Is there a change/ net transfer of energy?
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Does this question involve waves?
You will eventually see that the 1) and 2) essentially boil down to the same question - Will the object at time t2 be in the same state as the object at time t1? (Here by state i mean any measurement - acceleration, or velocity are the two most common ones at A level, though things like charge, capacitance or angular velocity).
This train of thought will allow you to solve at least 60% of the questions on the paper - the remaining 40% are about experiments, and those are all about memorisation, unfortunately.
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