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Class 9  »  Physics  »  Force and Laws of Motion

Balanced and Unbalanced Forces - UNSOLVED PRACTICE SET

Class 9

Chapter: Force and Laws of Motion | Topic: Balanced and Unbalanced Forces

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Study Material.
Class 9

BALANCED AND UNBALANCED FORCES - UNSOLVED PRACTICE SET

Topic: Balanced and Unbalanced Forces

Time: 40 mins | Marks: 30 | Difficulty: Medium

Multiple Choice Questions

Q1. A book lying still on a table has gravity pulling it down and normal reaction pushing it up. These forces are:

  1. Unbalanced — so the book accelerates
  2. Balanced — so the book remains stationary
  3. Both acting in the same direction
  4. Equal in magnitude but not in direction

Q2. When the net force on an object is not zero, the object will:

  1. Remain stationary
  2. Move at constant velocity
  3. Accelerate in the direction of the net force
  4. Decelerate always

Q3. In a tug-of-war, Team A pulls left with 600 N and Team B pulls right with 750 N. The net force is:

  1. 1350 N to the left
  2. 150 N to the right
  3. 150 N to the left
  4. 1350 N to the right

Q4. A car moves at a perfectly constant speed of 80 km/h on a straight highway. The forces on the car are:

  1. Unbalanced: engine force > friction
  2. Balanced: engine force = friction + air resistance
  3. Balanced: only gravity acts
  4. Unbalanced: only friction acts

Q5. An object at rest will remain at rest as long as:

  1. No force of any kind acts on it
  2. The forces acting on it are balanced (net force = 0)
  3. Gravity is zero
  4. It has no mass

Q6. A kite is hovering motionless in the sky. The forces of gravity (down), wind (up-ish), and string tension (down) are:

  1. Unbalanced
  2. Balanced (net force = 0)
  3. Only gravity acts
  4. Wind is not a force

Short Answer Questions

Q7. Define balanced and unbalanced forces. What is the effect of each on the state of motion of an object?

Q8. A heavy almari (wardrobe) is being pushed across a room at constant speed. Are the forces on it balanced or unbalanced? Explain with the forces involved.

Q9. Describe and label all forces on a person standing still on the ground. Explain why the person neither sinks into the ground nor flies upward.

Q10. A ball is kicked along a field, rolls for some distance, and then stops. Identify and explain whether the forces are balanced or unbalanced at each stage:
(a) just after the kick,
(b) while rolling,
(c) when stopped.

Q11. During a school sports tug-of-war, neither team moves for 15 seconds.
(a) What does this say about the net force?
(b) What change in force would allow one team to start winning?
(c) What type of forces are acting here?

Q12. Can balanced forces exist on an object that is already moving? Explain with one real-life example where this happens.

Long Answer Questions

Q14. A wooden block is placed on a rough table. A horizontal force is applied and slowly increased. Initially the block does not move. Then it starts sliding.
(a) Name the force preventing initial movement.
(b) Are forces balanced when stationary?
(c) What changed to make it slide?
(d) Once sliding at constant speed, are forces balanced?
(e) If applied force increases further, describe the new motion with reasoning.

Q15. Two children of different weights sit on a see-saw. Explain the entire motion using balanced and unbalanced forces:
(a) When neither side moves.
(b) When the heavier child's side goes down.
(c) What adjustment can make the see-saw balance even with unequal weights?
(d) Connect this to the concept of net torque / net force.
(e) Give one more everyday Indian example where balance and imbalance of forces are clearly visible.

Numerical / Application-Based Problems

Q16. Four forces act on a stationary block on a smooth surface: 40 N East, 25 N East, 30 N West, and F₄ West.
(a) For the block to remain stationary, find F₄.
(b) If F₄ = 50 N, find the net force and direction.
(c) If the block's mass is 6.5 kg, calculate its acceleration.
(d) In which direction does it accelerate?

Q17. A boat of mass 800 kg is drifting at a constant 2 m/s. The water resistance is 400 N.
(a) What must the engine force be for constant speed?
(b) The engine force is then increased to 650 N. Calculate the net force.
(c) Calculate the acceleration.
(d) What will the velocity be after 5 seconds of this acceleration?

Q18. Team Alpha pulls a rope with 1100 N and Team Beta pulls with 980 N in the opposite direction. The rope has a mass of 3 kg. 

(a) Calculate the net force on the rope. 

(b) In which direction does it accelerate?
(c) Calculate the acceleration of the rope. 

(d) If both teams increase their force by 200 N each, what happens to the net force? Is the rope still accelerating?


Total: 30 Marks | Time: 40 mins

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