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๐ฌ Think about it
In a tug of war, if both teams pull equally the rope stays put; if one pulls harder, it moves. Real objects usually feel more than one force at once. What is the combined effect? Let us explore balanced and unbalanced forces.
What are balanced forces?
- They are two forces equal in magnitude but opposite in direction.
- Their combined effect is zero, so the object does not move (or its motion does not change).
Example:
In tug of war, when both teams pull equally, the rope does not move.
What are unbalanced forces and net force?
- If forces on an object are not balanced, a non-zero net force acts.
- For opposite, unequal forces, net force = difference of the two, in the direction of the larger.
- For forces in the same direction, net force = sum of the two, in that direction.
Example:
If one tug-of-war team pulls harder, the rope moves toward the larger force.
โ Example 6.1
Two forces of 10 N and 6 N act on a block (Fig. 6.6). Find the magnitude and direction of the net force in each case.
(a) Same direction (right): Net force = 10 N + 6 N = 16 N, towards the right .
(b) Opposite, 10 N right and 6 N left: Net force = 10 N − 6 N = 4 N, towards the right .
(c) Opposite, 6 N right and 10 N left: Net force = 10 N − 6 N = 4 N, towards the left .
Important Points
- Balanced forces are equal and opposite; they cause no change in motion.
- Unbalanced forces leave a non-zero net force.
- Opposite forces subtract; same-direction forces add.
๐งฌ Pause and Ponder
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A weightlifter holds a barbell steady. List two forces on the barbell. Are they balanced?
The two forces are the Earth's gravitational pull (weight) downward and the lifter's upward push. When the barbell is steady they are balanced (equal and opposite). -
In arm-wrestling, when the arms tilt towards you, are the players' forces balanced? If not, who is stronger?
No — the arms move, so the forces are unbalanced. The player pushing the arms towards you (player S, in whose direction they tilt) is exerting the larger force.
๐ Ready to Go Beyond
- Sometimes forces act at an angle, not just parallel or opposite — you will learn to combine these in higher grades.
- Equal and opposite forces at the two ends of an extended object can make it rotate, like turning a tap or handlebar.
โ Test Yourself
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What are balanced forces?
View Answer
Two forces equal in magnitude but opposite in direction. -
Two opposite forces are 12 N and 8 N. What is the net force?
View Answer
4 N, in the direction of the 12 N force. -
Two 8 N forces act in the same direction. What is the net force?
View Answer
16 N, in that same direction.
Important Definitions
- Balanced forces — forces equal in magnitude and opposite in direction, giving zero net force.
- Net force — the single force that represents the combined effect of all forces on an object.
๐ NCERT Question 3 — Two blocks P and
Two blocks P and Q on a smooth surface — which experiences a net force?
View Answer →
๐ NCERT Question 4 — While practising for the
95 oarsmen row forward and 5 backward, each at 200 N — find the net force on the snake boat.
View Answer →
