Balanced and unbalanced forces
I can use the idea of resultant force to explain whether a change of speed occurs or not.
Balanced and unbalanced forces
I can use the idea of resultant force to explain whether a change of speed occurs or not.
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Lesson details
Key learning points
- Two forces of equal size, acting in opposite directions on an object, are balanced.
- The resultant force is the sum of the forces acting on the object, taking into account their direction.
- When forces are balanced there is no resultant force and no change in speed.
- When there are two forces acting in opposite directions, the resultant force acts in the direction of the bigger force.
- The greater the resultant force on a given object, the greater or faster the change in speed.
Keywords
Balanced forces - Two forces of equal size acting in opposite directions on an object, are balanced. They fully cancel each other out so no change is caused.
Unbalanced forces - Unbalanced forces do not fully cancel out.
Resultant force - The ‘force left over’ is called the resultant force. Resultant forces cause changes in speed.
Common misconception
The direction of the (resultant) force shows the direction of motion.
The direction of the resultant force shows the direction of the change (not the direction of motion). Forces make things change.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.What do forces cause?
Q2.Forces make things change. A larger force will cause a bigger or __________ change.
Q3.Which option is the best description of what it means when two things are balanced?
Q4.A person walks 9 metres straight forwards, then 4 metres straight backwards. The result of doing this is they are metres from where they started.
Q5.Forces can change an object's , direction or shape.
Q6.Are the forces on this car balanced or unbalanced?
Assessment exit quiz
6 Questions
Q1.Which image shows balanced forces?
Q2.The resultant force on this car is N.
Q3.Which pictures show a resultant force of 12 N? Tick as many as you think.
Q4.Which would cause an object to change speed?
Q5.The diagram only shows the forces acting on this car, not whether it is moving or not. Which of the following could be happening to this car?
Q6.This car is moving forwards. What happens next to this car, with these forces acting?
