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GCSE Physics forces and motion questions

Calculate average speed and acceleration, then use F = ma.

Practise

Resultant force and unit conversion

An object of constant mass 1380 g accelerates at 3.3 m s⁻². Calculate the magnitude of the resultant force in N. Give your answer to 3 significant figures.

Work through the calculation

Check intermediate steps, then use your unrounded working for the final answer. Each numerical check uses 3 significant figures. These steps provide support; the main answer is checked separately.

Step 1

Convert the mass from g to kg. Give your answer to 3 significant figures.

Show this step

Multiply the mass in grams by 10⁻³.

Answer: 1.38 kg (3 significant figures).

Step 2

Now calculate the final answer to the main question.

Show this step

Use the resultant force in F = ma. Put mass in kg.

Answer: 4.55 N (3 significant figures).

Treat the given values as exact unless an uncertainty is stated.

Use decimals or e notation, e.g. 4.2e-3. Enter the unit separately.

Hint

Use the resultant force in F = ma. Put mass in kg.

Worked solution
  1. Rule: F = ma.
  2. m = 1380 × 10-3 kg.
  3. F = ma = (1380 × 10-3) × 3.3 N.
  4. Answer: 4.55 N (3 significant figures).
Another question
Question type: Mixed practice
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Foundation and Higher: this set covers content common to both tiers. Some calculations need several steps.

Speed, acceleration and force

Average speed uses the total distance travelled and elapsed time. For acceleration, subtract the initial velocity from the final velocity, keeping the stated positive direction. F = ma uses the resultant force. Force diagrams, two-dimensional resolution and momentum are outside this set.

GCSE scope

AQA 8463: 4.5.1.4; 4.5.6.1.2, 4.5.6.1.5, 4.5.6.2.2; OCR Gateway J249: P2.1; P2.2; PM2.1i–ii, PM2.2i. Tasks cover the selected skills listed above.

AQA specification · OCR Gateway specification

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