Important Questions: Exploring Forces | Science Curiosity Class 8 - New NCERT PDF Download

Q1: What is the scientific definition of force, and how does it relate to everyday actions like pushing and pulling?
Ans: Force is a push or pull on an object. Everyday actions like pushing and pulling are examples of forces that can change the state of motion of objects.

Q2: Explain how forces are the result of interactions between objects. Provide examples from the chapter.
Ans: Forces occur when at least two objects interact with each other. For example, when a man pushes a stationary car, the car moves due to the interaction between the man and the car.

Q3: In a tug-of-war game, how does the team that applies a larger force win? Explain the concept of net force.
Ans: The team that applies a larger force in a tug-of-war game wins because the net force on the rope is greater in their direction. Net force is the difference between the forces applied in opposite directions.

Q4: How can a force change the state of motion of an object? Provide examples from sports like football, cricket, and volleyball.
Ans: A force can change the state of motion of an object by altering its speed or direction. For instance, in football, a player's kick changes the ball's speed and direction.

Q5: Is it always necessary for the application of force to result in a change in the state of motion? Explain with examples.
Ans: No, the application of force doesn't always lead to a change in the state of motion. For example, a heavy box may not move even if a force is applied, and no effect is observed when trying to push a wall.

Q6: Describe how force can change the shape of an object. Provide real-world examples from the chapter.
Ans: Force can change the shape of an object by applying pressure. For example, pressing an inflated balloon between your palms changes its shape.

Q7: Explain the concept of contact forces and provide examples from the chapter.
Ans: Contact forces require physical contact between the object and the force applier. Muscular force is an example, where muscles push or lift an object.

Q8:  What is friction, and how does it affect the motion of objects? Provide examples of friction from daily life.
Ans: Friction is a contact force that opposes the motion of objects. It acts in the direction opposite to the object's motion. Examples include a rolling ball coming to rest due to friction with the ground.

Q9: Describe non-contact forces with examples. Explain how magnets and electrostatic charges exert forces without direct contact.
Ans: Non-contact forces, like magnetic and electrostatic forces, act without physical contact. For example, magnets can attract or repel each other from a distance.

Q10: What is gravitational force, and how does it affect objects on Earth and in the universe?
Ans: Gravitational force is an attractive force that pulls objects towards each other. It keeps objects on Earth and influences their motion in the universe.

Q11. What is the SI unit of weight, and how is weight different from mass?
Ans:

• The SI unit of weight is newton (N), since weight is a force.

• Mass is the amount of matter in an object, measured in kilograms (kg), and it does not change with location.

• Weight is the force with which Earth (or another planet) attracts an object, and it depends on gravitational acceleration.

• Formula: Weight = Mass × Acceleration due to gravity (g).

Q12. How does a spring balance measure weight, and what are its two important features?
Ans:
A spring balance measures weight by the stretching of a spring when an object is suspended from its hook.

• Range: Maximum weight it can measure (e.g., 0–10 N).

• Least Count: The smallest weight it can measure, found by dividing the value between two main marks by the number of divisions.

Q13. Why does the same object weigh differently on Earth, Moon, and Jupiter? Give examples.
Ans:
Weight depends on the gravitational pull of the planet. Since gravity is different on each planet, weight changes though mass remains the same.
Example for a 1 kg object:

• Earth → 10 N

• Moon → 1.6 N

• Jupiter → 25.4 N

Q14. What is buoyant force? Explain with an example from daily life.
Ans:
Buoyant force is the upward force exerted by a liquid on an object immersed in it.
Example: When you push an empty, closed plastic bottle underwater, you feel an upward push, and the bottle bounces back to the surface when released.

Q15. State Archimedes’ Principle and explain one of its consequences.
Ans:
Archimedes’ Principle: An object fully or partially immersed in a liquid experiences an upward force equal to the weight of the liquid displaced by it.

• Consequence: If the weight of displaced liquid is equal to the object’s weight, it floats. If less, the object sinks.