Key points

  • Before you calculate, find the one condition in the text or diagram that the question depends on.
  • Checking the units of each option can often cross out two of them before you do any working.
  • When you review a graph question, write down which feature of the graph you misread.

Reading the question before you solve it

Knowing the formulas only gets you part of the way in ESAT Physics. Many questions put the important detail in a short block of text, a diagram or a graph. If you read it too quickly, you can solve the wrong problem perfectly.

The detail that matters is usually a condition. 'Moving at constant speed' tells you the resultant force is zero. 'A smooth surface' means you can ignore friction. 'The resistors are identical' lets you halve or double values without working out each current separately.

Before you write anything, ask yourself what quantity the question wants, which condition changes the problem, and what units the answer should have. Then decide whether it needs a calculation, a proportion or a line of reasoning with no numbers at all.

Using units to cross out options

Units are one of the quickest ways to remove answers that can't be right. They're most useful when the options are algebraic expressions.

Say a ball is dropped from rest at height h, and the question asks which expression gives the time it takes to reach the ground. The options might be √(2h/g), √(h/2g), 2h/g, √(2gh) and 2√(h/g).

The answer has to be in seconds. 2h/g has units of m ÷ m s⁻², which is s², so it goes. √(2gh) has units of m s⁻¹, which is a speed, so that goes too. The other three all give seconds and differ only by the number in front. One line of working, h = ½gt², gives t = √(2h/g).

Units also help with symbols that look alike. Lower-case p is momentum and capital P is power. E might be energy or electric field strength. If the units of your answer don't match what the question asked for, check which quantity you actually used.

When a proportion is quicker than a formula

If the arithmetic starts to look unpleasant, stop and ask whether the question only needs a ratio. Many ESAT Physics questions change one or two quantities and ask what happens to a third.

For example, a wire is swapped for one made of the same metal that's twice as long with half the diameter. Resistance is proportional to length divided by cross-sectional area. Halving the diameter makes the area a quarter, which multiplies the resistance by four, and doubling the length doubles it again. The new resistance is eight times the old one, and you never needed the resistivity.

If the options are in order and spread out, say 0.04, 0.4, 4, 40 and 400, a rough idea of size is enough. Work to one significant figure and pick the option that matches.

Reading graphs carefully

Before you read anything off a graph, check what each axis shows and its units. Then decide which feature the question is about: the gradient, the area under the line, an intercept, a maximum, or a change in how steep the curve is.

On a velocity-time graph, the gradient is acceleration and the area under the line is displacement. A question might show two objects and ask which travelled further. The one that reaches the higher speed isn't always the answer, so compare the areas.

A steeper line only means a bigger value if the axes are the way round you expect. If a graph has time on the vertical axis and distance on the horizontal one, the steeper line belongs to the slower object.

Reviewing graph questions

When you get a graph question wrong, write down exactly what happened. 'Revise graphs' won't help you next time. 'I read the height of the line when I needed the area under it' will, and so will 'I assumed steeper meant faster without checking the axes'.

After a few mocks, read these notes back. If the same sentence keeps appearing, practise a short set of questions on that one feature, then try it again inside a mixed timed set where nobody tells you what the topic is.

Planning for questions with a lot to read

Some Physics questions take longer to read than to solve. A module gives you 40 minutes for 27 questions, so a few long passages can take a big share of your time.

Decide before the test how you'll handle them. One approach is to read the last line first, so you know what you're looking for, and then read the rest. If you've spent about a minute and still don't know what the question needs, pick the most likely answer, flag it and come back if there's time.

Try this in your timed practice so it feels normal by the day of the test.