Resolving Forces and Free Body Diagrams
Build confidence in Resolving Forces and Free Body Diagrams for GCSE Physics with this free worksheet and full mark scheme — Higher-tier exam-style questions with worked answers for AQA, Edexcel and OCR. A single force can be resolved into two perpendicular components, and scale diagrams can be used to find a resultant.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
This is a Higher tier only topic, so there's no Foundation paper — only the Higher worksheet and mark scheme below.
Topic overview
A single force can be resolved into two components acting at right angles to each other. The two components together have the same effect as the single force. This is a Higher-only topic.
This is done using a scale drawing. The force is drawn as an arrow of scaled length in the correct direction, and lines are drawn from its tip parallel to the two chosen directions, usually horizontal and vertical.
A free body diagram shows all the forces acting on a single object, drawn as arrows from a point representing the object. The length of each arrow shows the magnitude and its direction shows the direction of the force. Only forces acting on the object are drawn, not forces the object exerts on others.
Revision notes
Resolving a force
A single force can be resolved into two components acting at right angles.
The two components together have exactly the same effect as the original single force. This is the reverse of finding a resultant.
Using scale drawings
Choose a scale, such as 1 cm to 10 N, and draw the force as an arrow of the correct length and direction.
Draw lines from the tip of the arrow parallel to the two chosen directions to complete a rectangle. Measure the sides and convert back using the scale.
Free body diagrams
A free body diagram shows all the forces acting on a single object.
Each force is drawn as an arrow from a point representing the object, with length showing magnitude and direction showing direction. Only forces acting ON the object are included.
Key points
- A force can be resolved into two perpendicular components.
- The components have the same effect as the original force.
- Scale drawings are used to resolve forces.
- State the scale used, such as 1 cm to 10 N.
- A free body diagram shows all forces on one object.
- Arrow length shows magnitude and direction shows direction.
Worked examples
Example 1
Explain what is meant by resolving a force. [2 marks]
Model answer
Resolving means replacing a single force with two components acting at right angles to each other (1 mark), which together have exactly the same effect as the original force (1 mark).
Example 2
Describe what a free body diagram shows. [2 marks]
Model answer
It shows all the forces acting on a single object (1 mark), each drawn as an arrow whose length represents the magnitude and whose direction represents the direction of the force (1 mark).
Example 3
State two things that must be included when using a scale drawing to resolve a force. [2 marks]
Model answer
The scale used, such as 1 cm representing 10 N (1 mark), and arrows drawn to the correct length and in the correct direction (1 mark).
Common mistakes
Drawing forces the object exerts on others.
A free body diagram shows only forces acting ON the object.
Forgetting to state the scale.
Without it the drawing cannot be interpreted or marked.
Resolving into components that are not perpendicular.
The two components must be at right angles to each other.
Drawing arrows of arbitrary length.
Length must be proportional to the magnitude of the force.
Exam tips
- Always state the scale on a scale drawing.
- Draw arrows to scale and in the correct direction.
- Include only forces acting on the object.
- Remember this is a Higher-only topic.
Key terms
- Resolve
- To split a force into two perpendicular components.
- Component
- One of the two perpendicular parts of a resolved force.
- Free body diagram
- A diagram showing all forces acting on one object.
- Scale drawing
- A drawing where lengths represent magnitudes.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.