Adding forces along a line, balanced forces, free body diagrams, and (Higher) scale drawings and resolving a force into two components.
What you will learn
- Find the resultant of forces along a line
- Draw and read free body diagrams
- Use a scale drawing to add two forces at an angle (Higher)
- Resolve a force into two components (Higher)
One force that does the same job
When several forces act on an object, the resultant force is the single force that would have the same effect.
Along a line: forces the same way add; forces in opposite directions subtract. The resultant points the way of the bigger total.
- A crate is pushed right with 200 N and 150 N; friction is 270 N to the left
- right: 200 + 150 = 350 N
- resultant = 350 − 270 = 80 N to the right
If the forces balance, the resultant is zero. The object stays still, or keeps moving at a steady speed in a straight line.
That gives a way to measure friction: pull an object along at a steady speed with a newtonmeter. The forces balance, so the reading equals the friction.
The rest of this lesson and its 9 practice questions are locked.
In this lesson
- One force that does the same job
- Free body diagrams
- Forces at an angle (Higher)
- Try it: Split the weight on a slope
- Try it: Your first resultant
9 practice questions, marked as you go; about 25 minutes in all.
Key terms
Resultant force, Scale drawing
In this unit: Forces, work, elasticity, moments and pressure
Weight and resultant forces, work done, stretching springs and their required practical, moments, levers and gears, and pressure in fluids.
- Forces, mass and weight
- Resultant forces and free body diagrams
- Work done and energy transfer
- Springs, elasticity and the force-extension practical
- Moments, levers and gears
- Pressure in fluids