You are here
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.
Are the forces on an object balanced?
Forces on an object
Combined, do they cancel?
1. Balanced
Net force is zero
Example:
Steady tug of war
2. Unbalanced
A net force is left
Example:
Rope moves to one side
What are balanced forces?
Balanced forces
Equal in magnitude
the same strength on both sides
Opposite in direction
they pull against each other
↓
Balanced forces
cancel out — net force = 0, so the rope in a tug of war does not move.
- 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?
Net force
Net
what is left over after the forces are combined
force
the single force that has the same effect as all of them
↓
Net force
= the combined effect of every force acting. If it is not zero, the motion changes.
Forces in
opposite
directions
Forces in the
same
direction
Subtract the magnitudes
Add the magnitudes
10 N − 6 N =
4 N
10 N + 6 N =
16 N
Net force points along the
larger
force
Net force points the
same
way as both
- 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
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
-
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
-
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 Q
Two blocks P and Q on a smooth horizontal surface are shown in Fig. 6.36a and Fig. 6.36b. Two forces of magnitudes 4 N and 5 N are acting in opposite directions on block P, while block Q is moving with a constant velocity.
Which of the following statement is correct?
(i) P experiences a net force and Q does not experience a net force.
(ii) P does not experience a net force and Q experiences a net force.
(iii) Both P and Q experience a net force.
(iv) Neither P nor Q experiences a net force.
View Answer →
Which of the following statement is correct?
(i) P experiences a net force and Q does not experience a net force.
(ii) P does not experience a net force and Q experiences a net force.
(iii) Both P and Q experience a net force.
(iv) Neither P nor Q experiences a net force.
๐ NCERT Question 4 — While practising for the snake
While practising for the snake boat race (
Vallum kalli
in Kerala), 100 oarsmen are rowing a boat together. Out of these, 95 row backwards to propel the boat forward. But by mistake, 5 oarsmen row in the opposite direction. If each oarsman applies a horizontal force of 200 N, what is the net force on the snake boat? (Ignore drag forces, air friction, etc.)
View Answer →
