Class 9 Chapter 8 Force and Laws of Motion

 Class 9 Chapter 8 Force and Laws of Motion

Q: What is required to accelerate the motion of an object or change its direction? A: An unbalanced force is required to accelerate an object or change its direction of motion.

Q: What are balanced forces? A: Balanced forces are equal and opposite forces that do not change the state of rest or of motion of an object.

Q: What is inertia? A: Inertia is the natural tendency of an object to resist a change in its state of rest or of uniform motion.

Q: How is the inertia of an object measured quantitatively? A: The inertia of an object is measured by its mass.

Q: What does Newton's first law of motion state? A: It states that an object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied force.

Q: What is momentum? A: Momentum is the product of an object's mass and its velocity ($p = mv$).

Q: What is the SI unit of momentum? A: The SI unit of momentum is kilogram-metre per second (kg m s⁻¹).

Q: What does Newton's second law of motion state? A: It states that the rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of the force.

Q: What is the mathematical formula for force according to the second law of motion? A: Force is the product of mass and acceleration ($F = ma$).

Q: What is the SI unit of force? A: The SI unit of force is kg m s⁻², which is also known as the newton (N).

Q: What does Newton's third law of motion state? A: It states that to every action, there is an equal and opposite reaction.

Q: Do action and reaction forces act on the same object? A: No, action and reaction forces always act on two different objects simultaneously.

Q: What force always opposes the motion of objects? A: The force of friction always opposes the motion of objects.