# Balanced and Unbalanced Forces

#### Students’ Learning Outcomes

·         Differentiate between balanced and unbalanced forces.
·         Describe the effects of balanced and unbalanced forces on the motion of an object.
Information for Teachers
·         Forces occur in pairs and can be either balanced or unbalanced.
·         Balanced forces don’t cause a change in motion. They are equal in magnitude and opposite in direction.
·         Unbalanced forces always cause a change in motion. They are not equal and opposite.

#### Material / Resources

Toy car, wooden block, string, scissors, textbook

#### Worm up Activity:

·         Ask the students: What will happen when you pull an object?
(Students’ response: It will moves towards us.)
·         What will happen when you push an object?
(Students’ response: It moves away)
·         What will happen when you push or pull an object at rest on its opposite sides with equal forces?
(Students’ response: It doesn’t move)
·         Show the students a toy car placed on a table.
·         Ask a student: push the car towards right with your one hand. In which direction does the car move?
(Students’ response: Car moves towards right).
·         Ask the same student: Now push the car towards left with your other hand. In which direction does the car move now?
(Students’ response:  car moves towards left)
·         Now ask to push the car towards right with one hand and at the same time push it towards left with the other hand. What will be the motion of car?
(Students’ response: Car doesn’t move).
·         Draw out the result that if two forces acting on a body produce no motion in it, the forces are said to be balanced. If the two forces produce motion in the body, the forces are said to be unbalanced. If two forces balance each other, they must be equal and opposite in directions.

#### Activity 1

Hang a wooden block with the help of thread and ask the students:
·         How many forces are acting on the block?
(Students’ response: two forces).
·         What force is acting downwards on a block?
(Students’ response:  Weight of the block).
·         What forces is acting upwards on the block?
(Students’ response: Force applied by hand through the thread pulling the block upwards)
·         Draw a diagram of the block, the thread and hand on the board showing the two arrows representing the two forces and ask:
·         Why is the block at rest?
(Students’ response: The two forces are balanced).
(Students’ response: The block will fall down).
·         Draw a diagram of the block and the thread on the board after the thread has been cut, showing an arrow that represents one force and ask:
·         How many force are acting on the block after the thread has been cut?
(Students’ response: One force acting downward).
·         Is the force balanced or unbalanced?
(Students’ response: Unbalanced)
·         Inform the students that unbalanced force causes the object to move.

#### Sum up / Conclusion

Ask the students: What have you learned today and write the conclusions on the board:
·         When two forces acting on a body produce no motion in it, the force are said to be balanced.
·         When two forces acting on a body produce motion in it, the forces are said to be unbalanced.
·         If two forces balance each other, they must be equal and opposite in directions.

#### Assessment

·         Tell the students that suppose ‘there is a book on a table. Ask them:
——-What forces are acting on the book?
——To draw the diagram on their notebook and show the forces acting on the book with the
help of arrows.
·         Ask them to draw the arrows in the same way by giving various examples from daily life e. g. a bicycle, a table lamp. A computer and a chair when you are sitting in it.
·         Involve the students in solving the questions given at the end of chapter / unit in textbook.