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Q1. The inherent property of an object that causes it to resist any change in its state of rest or uniform motion is called:
Inertia is the natural property of an object by which it opposes any change in its state of rest or uniform motion. This is the fundamental concept behind Newton’s First Law of Motion.
Q2. Between a football and a stone of the same size, which one has greater inertia?
Inertia depends on mass. A stone has greater mass than a football of the same size because stone is denser. Therefore, the stone has greater inertia and resists changes in its state of motion more strongly.
Q3. Momentum is mathematically defined as the product of:
Momentum (p) is defined as the product of mass (m) and velocity (v). So p = m × v. It is a vector quantity having both magnitude and direction.
Q4. The phenomenon where you fall forward when a moving bus stops suddenly is best explained by:
When the bus stops suddenly, your body tends to continue moving forward due to its inertia. This is why you lurch forward. Your body resists the change in motion caused by the bus stopping.
Q5. What is the SI unit of momentum?
Momentum is mass × velocity. The SI unit of mass is kg and velocity is m/s, so the unit of momentum is kg·m/s. It can also be written as N·s (Newton-second).
Q6. Newton’s Second Law of Motion states that force is directly proportional to the:
Newton’s Second Law states that the net force acting on an object is equal to the rate of change of its momentum. Mathematically, F = dp/dt, where p is momentum.
Q7. For an object of constant mass, Newton’s Second Law can be expressed as:
For an object with constant mass, Newton’s Second Law simplifies to F = ma, where F is the net force, m is the mass, and a is the acceleration produced.
Q8. The SI unit of force, the newton, is named after:
The SI unit of force is named the newton (N) in honour of Sir Isaac Newton, who formulated the Three Laws of Motion and made significant contributions to classical mechanics.
Q9. Momentum is classified as a vector quantity because it has:
Momentum is a vector quantity because it has both magnitude (mass × speed) and direction (same as the direction of velocity). This is why momentum can be positive or negative depending on the direction chosen.
Q10. For an object initially at rest (u = 0) to remain at rest, the net force acting on it must be:
According to Newton’s First Law, an object at rest remains at rest unless acted upon by a net external force. So for it to remain at rest, the net force must be zero.
Q11. The tendency of a stationary object to remain at rest is due to its:
Inertia is the property that causes a stationary object to resist any change in its state of rest. This is why an object at rest tends to stay at rest unless a force acts on it.
Q12. A moving truck is more dangerous than a stationary truck primarily because it possesses:
A moving truck has significant momentum (mass × velocity). This large momentum makes it difficult to stop and can cause great damage in a collision. A stationary truck has zero momentum.
Q13. Even a small bullet can cause significant damage because:
Although a bullet has small mass, its very high velocity gives it significant momentum. Additionally, this momentum is concentrated over a very small area, creating high pressure and causing significant damage.
Q14. A greater force is experienced when:
Force is the rate of change of momentum (F = Δp/Δt). If momentum changes rapidly (over a short time), the force experienced is greater. This is why quick impacts are more forceful.
Q15. A cricket fielder pulls their hands backward while catching a fast ball to:
By pulling hands backward, the fielder increases the time over which the ball’s momentum changes to zero. According to F = Δp/Δt, increasing the time reduces the force on the hands, preventing injury.
Q16. Falling on sand is less painful than falling on concrete because sand:
Sand compresses upon impact, increasing the stopping time. Since force = change in momentum/time, increasing the time reduces the force experienced by the body, making the fall less painful.
Q17. The direction of an object’s momentum vector is always the same as its:
Momentum (p = mv) is a vector that points in the same direction as the velocity of the object. Since mass is a scalar, multiplying it by velocity gives a vector in the direction of velocity.
Q18. According to F = m × a, if the net force on an object increases while mass stays constant:
From F = ma, we get a = F/m. For constant mass, acceleration is directly proportional to force. So if force increases, acceleration also increases proportionally.
Q19. For a constant applied force, if the mass of an object increases:
From a = F/m, for constant force, acceleration is inversely proportional to mass. So if mass increases, acceleration decreases. Heavier objects accelerate less under the same force.
Q20. The potential impact or damage caused by a moving object depends on both its:
The impact or damage depends on the momentum of the object, which is the product of mass and velocity. A heavy object moving fast has the greatest potential for damage.
Q21. When an unbalanced net force acts on an object, it causes a change in the object’s:
An unbalanced force causes a change in velocity, which results in a change in momentum (since momentum = mass × velocity). The mass and shape do not change due to force.
Q22. The inertia of an object depends fundamentally on its:
Inertia is directly proportional to mass. The greater the mass of an object, the greater its inertia. Volume, shape, and color do not affect inertia.
Q23. A loaded truck requires more braking force to stop than a small car because:
A loaded truck has much larger mass, giving it greater inertia and momentum for the same speed. This requires a greater braking force to bring it to a stop.
Q24. The most common mathematical expression of Newton’s Second Law is:
For constant mass, Newton’s Second Law is expressed as F = ma, where F is the net force, m is mass, and a is acceleration. This is the most commonly used form.
Q25. When a constant net force is applied to an object of constant mass, it produces:
From F = ma, if F is constant and m is constant, then acceleration a is also constant. This means the object’s velocity changes at a uniform rate.
Q26. The momentum of an object increases when:
Momentum p = mv. For constant mass, momentum increases when velocity increases. An increase in velocity means the object is speeding up.
Q27. The rate at which momentum changes depends inversely on:
Force = change in momentum / time (F = Δp/Δt). For a given change in momentum, if the time is longer, the force is smaller. So rate of change of momentum is inversely proportional to time.
Q28. According to Newton’s First Law, when the net force on an object is zero, its velocity:
Newton’s First Law states that an object continues in its state of rest or uniform motion unless acted upon by a net external force. So if net force is zero, velocity remains constant.
Q29. Padded dashboards in cars reduce injury risk because the padding:
Padding increases the time over which the passenger’s momentum changes during a collision. This reduces the force on the passenger (F = Δp/Δt), preventing serious injuries.
Q30. A standing passenger falls backward when a bus starts suddenly due to:
When the bus starts moving, the lower body moves with the bus, but the upper body tends to remain at rest due to inertia. This causes the passenger to fall backward.
Q31. When a moving bus stops suddenly, passengers continue moving forward due to:
When the bus stops, the passengers’ bodies tend to continue moving forward because of their inertia of motion. This is why they lurch forward when brakes are applied suddenly.
Q32. To produce the same acceleration, a greater force is required for:
From F = ma, for the same acceleration, force is directly proportional to mass. So a larger mass requires a greater force to produce the same acceleration.
Q33. Quantify and calculate force
Force can be quantified and calculated using Newton’s Second Law: F = m × a. By knowing the mass and acceleration of an object, we can calculate the net force acting on it.
Q34. The momentum of an object becomes zero when:
Momentum p = m × v. If velocity v = 0, then momentum is zero regardless of mass. An object at rest has zero momentum.
Q35. A large force applied over a very short time interval produces:
Impulse = Force × Time = Change in momentum. Even if time is short, a large force can produce a significant change in momentum. This is why sharp impacts can be very effective.
Q36. When an object’s velocity increases while mass remains constant, its momentum:
Since p = mv, for constant mass, momentum is directly proportional to velocity. So if velocity increases, momentum increases proportionally.
Q37. One newton (1 N) of force is equivalent to:
One newton is defined as the force required to give a mass of 1 kilogram an acceleration of 1 metre per second squared. So 1 N = 1 kg·m/s².
Q38. In the equation p = mv, the symbol ‘p’ represents:
In physics, the symbol ‘p’ is commonly used to represent momentum. The equation p = mv defines momentum as the product of mass (m) and velocity (v).
Q39. The change in an object’s momentum (Δp) is equal to:
Impulse = Force × Time = Change in momentum (Δp). This is known as the impulse-momentum theorem. A force applied over a time interval changes the object’s momentum.
Q40. Which two factors determine the magnitude of an object’s momentum?
The magnitude of momentum depends on the mass of the object and its velocity (p = mv). Both factors are equally important in determining momentum.
Q41. According to F = ma, if force increases while mass remains constant:
From F = ma, a = F/m. For constant mass, acceleration is directly proportional to force. So if force increases, acceleration increases by the same proportion.
Q42. If a car takes longer to come to a stop during braking, the average braking force is:
The change in momentum is fixed (from initial speed to zero). If time increases, the force decreases because F = Δp/Δt. This is why gradual braking is smoother.
Q43. A high-speed object poses greater danger primarily because it carries:
A high-speed object has high momentum (p = mv). High momentum means it is harder to stop and can cause greater damage upon impact.
Q44. To minimize injury during an impact, the time over which stopping occurs should be:
Increasing the stopping time reduces the force experienced (F = Δp/Δt). This is why airbags, seat belts, and cushioning materials are designed to increase impact time and reduce injury.
Q45. If an object’s mass doubles while its velocity remains constant, its momentum:
Momentum p = mv. If mass doubles and velocity is constant, momentum also doubles because they are directly proportional.
Q46. Momentum is correctly classified as a vector quantity because it:
Momentum is a vector quantity because it has both magnitude (mass × speed) and direction (same as velocity). This is why changes in direction also mean changes in momentum.
Q47. When an object’s acceleration is measured to be zero, the net force acting on it must be:
According to F = ma, if acceleration a = 0, then the net force F must also be zero. This means the forces acting on the object are balanced.
Q48. A 5 kg object experiencing an acceleration of 2 m/s² has a net force acting on it of:
Using F = ma, F = 5 kg × 2 m/s² = 10 N. So a net force of 10 N is acting on the object.
Q49. The constant ‘k’ in the general form of Newton’s Second Law (F = kma) equals 1 when:
In SI units, the constant k equals 1, giving F = ma. If other unit systems are used (like imperial units), the constant may be different. The choice of units determines the value of k.
Q50. The momentum of an object changes only when:
According to Newton’s Second Law, an unbalanced net force causes a change in momentum. If no force or balanced forces act, momentum remains constant. Mass does not spontaneously change.