Higher tier: Summary
- When forces on an object are balanced;
- the object will move at a steady speed in a straight line, or
- remain at rest.
- The resultant force is the single force that has the same effect as two or more forces acting together.
- The resultant of two or more forces that act in the same direction is found by adding their sizes together.
- The resultant of two forces that act in the opposite direction is found by subtracting their sizes.
- Newton’s second law tells us that when a resultant force acts on an object it accelerates. That means a resultant force makes an object:
- speed up or slow down, and/or
- change direction.
- Resultant force = mass × acceleration or F = ma.
- If the resultant force acting on an object is in the same direction as it is moving, it speeds up or accelerates.
- If the resultant force acting on an object is in the opposite direction to which it is moving it slows down or decelerates. Eventually it will come to rest.
