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📘 Study MCQs
Q1. The inherent property of an object that causes it to resist any change in its state of rest or uniform motion is called:
• Velocity
• Acceleration
• Momentum
• Inertia
Answer: Inertia
Think of a heavy boulder at rest. It’s hard to get it moving. Once rolling, it’s hard to stop. This isn’t because it’s stubborn, but because all objects have a natural tendency to keep doing what they’re already doing—this tendency is called inertia. It’s why you feel pushed back into your seat when a car accelerates, or lurch forward when it brakes.
Q2. Between a football and a stone of the same size, which one has greater inertia?
• The football
• The stone
• Both have equal inertia
• Neither has inertia
Answer: The stone
Inertia depends on mass, not size. A stone is much denser than a football, so a stone of the same size (volume) contains much more mass. More mass means more inertia. The stone would be harder to start moving from rest and harder to stop once it’s moving compared to the football.
Q3. Momentum is mathematically defined as the product of:
• Mass and acceleration
• Mass and velocity
• Force and time
• Velocity and time
Answer: Mass and velocity
Momentum is a measure of how much “oomph” a moving object has. It combines both how much stuff is moving (mass) and how fast it’s moving (velocity). The formula is p = m × v. A slow-moving truck (large mass, small velocity) and a fast-moving bullet (small mass, large velocity) can both have high momentum.
Q4. The phenomenon where you fall forward when a moving bus stops suddenly is best explained by:
• The friction between your shoes and the bus floor
• Your inertia resisting the change in motion
• The aerodynamics of the bus interior
• The weight of your body
Answer: Your inertia resisting the change in motion
You and the bus are moving forward together. When the brakes stop the bus, an unbalanced force acts on the bus. However, no such horizontal force acts directly on your body. Due to inertia—your tendency to continue moving—your body keeps moving forward even as the bus stops beneath you.
Q5. What is the SI unit of momentum?
• Newton (N)
• Kilogram-meter per second (kg·m/s)
• Joule (J)
• Watt (W)
Answer: Kilogram-meter per second (kg·m/s)
Since momentum = mass × velocity, and mass is measured in kilograms (kg) while velocity is in meters per second (m/s), the unit for momentum becomes kilogram-meter per second (kg·m/s). There’s no special name for this unit; it’s simply the product of the units of its components.
Q6. Newton’s Second Law of Motion states that force is directly proportional to the:
• Rate of change of momentum
• Rate of change of inertia
• Rate of mass increase
• Rate of velocity decrease
Answer: Rate of change of momentum
This is how Newton originally expressed his law. It means that the net force acting on an object equals how quickly its momentum is changing. Mathematically: Force = (Final momentum – Initial momentum) ÷ Time. If an object’s momentum changes quickly (like in a crash), a large force is involved.
Q7. For an object of constant mass, Newton’s Second Law can be expressed as:
• F = m × v
• F = m × a
• F = v ÷ t
• F = m ÷ v
Answer: F = m × a
Since momentum (p) = m × v, and if mass (m) is constant, then the rate of change of momentum = m × (rate of change of v) = m × a, where ‘a’ is acceleration. So the familiar form F = m × a is a special case of the more general law, valid when mass doesn’t change.
Q8. The SI unit of force, the newton, is named after:
• Galileo Galilei
• Albert Einstein
• Isaac Newton
• James Watt
Answer: Isaac Newton
The newton (symbol: N) honors Sir Isaac Newton, who formulated the laws of motion and universal gravitation. One newton is defined as the force needed to accelerate a one-kilogram mass by one meter per second squared (1 N = 1 kg·m/s²).
Q9. Momentum is classified as a vector quantity because it has:
• Only numerical value (magnitude)
• Only direction
• Both magnitude and direction
• Neither magnitude nor direction
Answer: Both magnitude and direction
Like velocity, momentum has both size (how much) and direction (which way). A 5 kg ball moving east at 2 m/s has different momentum than the same ball moving west at 2 m/s. When we calculate total momentum in collisions, we must consider both magnitude AND direction.
Q10. For an object initially at rest (u = 0) to remain at rest, the net force acting on it must be:
• 5 N
• 10 N
• 0 N
• A very large force
Answer: 0 N
Newton’s First Law states that an object at rest stays at rest unless acted upon by a net force. If the net force (the vector sum of all forces) is zero, there’s no push or pull to start the object moving. It will remain stationary indefinitely.
Q11. The tendency of a stationary object to remain at rest is due to its:
• Applied force
• Velocity
• Inertia
• Momentum
Answer: Inertia
Inertia is the property that resists changes in motion. For an object at rest, this means it resists starting to move. You experience this when trying to push a heavy piece of furniture—it doesn’t want to start moving because of its inertia.
Q12. A moving truck is more dangerous than a stationary truck primarily because it possesses:
• Lower velocity
• No inertia
• Significant momentum
• Less mass
Answer: Significant momentum
A moving truck has both mass and velocity, giving it momentum (p = m × v). To stop this momentum, a force must be applied over time. In a collision, this momentum change happens very quickly, resulting in enormous forces that can cause severe damage and injury.
Q13. Even a small bullet can cause significant damage because:
• It has no mass
• Its speed is actually quite low
• Its momentum is concentrated in a very small area
• It has no velocity
Answer: Its momentum is concentrated in a very small area
While a bullet has small mass, its extremely high velocity gives it considerable momentum. More importantly, when it strikes, all that momentum is transferred to a tiny area (the bullet tip) over an extremely short time. This creates tremendous pressure and force, causing penetration and damage.
Q14. A greater force is experienced when:
• Momentum changes slowly over a long time
• The time of impact is very long
• Momentum changes very rapidly
• Mass is decreasing gradually
Answer: Momentum changes very rapidly
From Newton’s Second Law: Force = Change in momentum ÷ Time. For a given change in momentum, if the time (Δt) is very small, the force (F) becomes very large. This is why hitting a wall hurts more than falling onto a mattress—the wall stops you almost instantly (small Δt = large F).
Q15. A cricket fielder pulls their hands backward while catching a fast ball to:
• Increase the force on their hands
• Reduce the time of catch
• Increase the time of catch and reduce the force
• Change the ball’s direction dramatically
Answer: Increase the time of catch and reduce the force
By moving hands backward, the fielder increases the time (Δt) over which the ball’s momentum changes to zero. Since Force = Δp/Δt, a larger Δt means a smaller average force on the hands. This prevents injury and makes it easier to secure the catch without the ball bouncing out.
Q16. Falling on sand is less painful than falling on concrete because sand:
• Is softer in texture
• Increases the time over which you stop
• Is rougher than concrete
• Reduces gravitational pull during fall
Answer: Increases the time over which you stop
When you hit sand, your body sinks in slightly, taking more time to come to a complete stop compared to hitting unyielding concrete. A longer stopping time (Δt) means a smaller average stopping force (F = Δp/Δt), resulting in less pain and injury.
Q17. The direction of an object’s momentum vector is always the same as its:
• Mass direction
• Net force direction
• Velocity direction
• Acceleration direction
Answer: Velocity direction
Since momentum = mass × velocity, and mass is a positive scalar, momentum points in the exact same direction as velocity. If a car is moving northeast, its momentum vector also points northeast. This is why we use arrows to represent both velocity and momentum.
Q18. According to F = m × a, if the net force on an object increases while mass stays constant:
• Acceleration decreases
• Acceleration increases
• Acceleration becomes zero
• Acceleration becomes negative
Answer: Acceleration increases
The equation shows a direct proportionality: F ∝ a when m is constant. Double the force, and you double the acceleration. Triple the force, triple the acceleration. This makes sense—push harder on a shopping cart (same mass), and it speeds up more quickly.
Q19. For a constant applied force, if the mass of an object increases:
• Acceleration increases
• Acceleration decreases
• Acceleration doubles
• Acceleration remains constant
Answer: Acceleration decreases
From a = F/m, acceleration is inversely proportional to mass when force is constant. More mass means more inertia to overcome. A given engine force will accelerate a small car quickly but a loaded truck much more slowly because the truck has more mass.
Q20. The potential impact or damage caused by a moving object depends on both its:
• Mass alone
• Velocity alone
• Mass and velocity
• Shape alone
Answer: Mass and velocity
Damage results from the transfer of momentum and energy during impact. Both mass (how much stuff) and velocity (how fast it’s moving) matter. A slow-moving train (high mass) and a fast-moving bullet (high velocity) can both cause severe damage, but for different combinations of mass and velocity.
Q21. When an unbalanced net force acts on an object, it causes a change in the object’s:
• Mass
• Shape
• Momentum
• Temperature
Answer: Momentum
This is the essence of Newton’s Second Law: F_net = Δp/Δt. An unbalanced force causes the momentum to change over time. This change in momentum manifests as acceleration—a change in velocity (speed, direction, or both).
Q22. The inertia of an object depends fundamentally on its:
• Volume
• Mass
• Shape
• Color
Answer: Mass
Inertia is quantified by mass. More mass = more inertia. A 10 kg bowling ball has more inertia than a 1 kg soccer ball—it’s harder to start moving, harder to stop, and harder to change its direction. Volume alone doesn’t determine inertia; density matters too.
Q23. A loaded truck requires more braking force to stop than a small car because:
• Its mass is much larger
• It has lower velocity
• It has less inertia
• It has smaller momentum
Answer: Its mass is much larger
Stopping means changing momentum to zero. A truck has much more mass than a car, so even at the same speed, it has much more momentum (p = m × v). To bring this larger momentum to zero in the same stopping distance requires a proportionally larger braking force.
Q24. The most common mathematical expression of Newton’s Second Law is:
• F = m × v
• F = m × a
• F = p × t
• F = v/t
Answer: F = m × a
For objects with constant mass, this is the most practical form. It tells us the net force equals mass times acceleration. This formula allows us to calculate the force needed to produce a desired acceleration, or the acceleration resulting from a known force.
Q25. When a constant net force is applied to an object of constant mass, it produces:
• Zero acceleration
• Constant velocity
• Constant acceleration
• Decreasing mass
Answer: Constant acceleration
From F = m × a, if F is constant and m is constant, then ‘a’ must also be constant. The object’s velocity will change at a steady rate. For example, an object in free fall near Earth’s surface experiences approximately constant gravitational force, giving it constant acceleration (g ≈ 9.8 m/s²).
Q26. The momentum of an object increases when:
• Force acting on it decreases
• Its velocity increases
• Its mass decreases
• Acceleration becomes zero
Answer: Its velocity increases
Since p = m × v, if mass stays constant, increasing velocity directly increases momentum. If you double the velocity, you double the momentum. This is why a car going 60 km/h has twice the momentum of the same car going 30 km/h.
Q27. The rate at which momentum changes depends inversely on:
• The time over which the change occurs
• The surface area
• The temperature
• The volume
Answer: The time over which the change occurs
Rate of change of momentum = Δp/Δt. For a fixed change in momentum (Δp), if the change happens over a longer time (Δt), the rate is smaller. If it happens almost instantly (very small Δt), the rate is enormous. This explains why airbags work—they increase Δt to decrease the rate of momentum change.
Q28. According to Newton’s First Law, when the net force on an object is zero, its velocity:
• Becomes zero immediately
• Remains constant
• Increases steadily
• Reverses direction
Answer: Remains constant
This is the law of inertia. Zero net force means no acceleration. No acceleration means velocity doesn’t change—it stays exactly as it was. If it was at rest (v=0), it stays at rest. If it was moving at 5 m/s east, it continues at 5 m/s east.
Q29. Padded dashboards in cars reduce injury risk because the padding:
• Stops passengers instantly
• Increases the impact force
• Increases the stopping time
• Reduces the passenger’s mass
Answer: Increases the stopping time
During a collision, the padding compresses, which takes more time to bring a passenger to rest compared to a hard dashboard. From F = Δp/Δt, increasing Δt decreases the average force F on the passenger’s body, reducing the risk of serious injury.
Q30. A standing passenger falls backward when a bus starts suddenly due to:
• Gravity pulling backward
• The bus pushing backward
• The inertia of the passenger’s upper body
• Air pressure changes
Answer: The inertia of the passenger’s upper body
The passenger’s feet are in contact with the bus floor. When the bus starts forward, the feet are pulled forward with it. However, the passenger’s upper body, due to inertia of rest, tends to stay where it was. This causes the body to lean or fall backward relative to the bus.
Q31. When a moving bus stops suddenly, passengers continue moving forward due to:
• Inertia of motion
• Air rushing forward
• Gravity decreasing
• Friction with seats
Answer: Inertia of motion
Both bus and passengers are moving forward. When brakes stop the bus, an unbalanced force acts on the bus. No such horizontal force acts directly on passengers. Their inertia of motion—the tendency to continue moving—makes them keep going forward as the bus stops beneath them.
Q32. To produce the same acceleration, a greater force is required for:
• A smaller mass
• A larger mass
• A stationary body
• A massless object
Answer: A larger mass
From F = m × a, for a fixed acceleration (a), force (F) is directly proportional to mass (m). To give a truck (large m) the same acceleration as a bicycle (small m), you need a much larger force. The truck’s greater inertia requires more force to overcome.
Q33. Quantify and calculate force
• Measure distance traveled
• Calculate work done
Answer: Quantify and calculate force
The law F = m × a gives us an operational definition of force. If we can measure an object’s mass and the acceleration it experiences, we can calculate the net force acting on it. This allows engineers to design structures, vehicles, and safety systems with precise force calculations.
Q34. The momentum of an object becomes zero when:
• Its mass is zero
• Its velocity is zero
• Time is zero
• Force is zero
Answer: Its velocity is zero
Since p = m × v, if v = 0, then p = 0 regardless of mass. A stationary truck, no matter how massive, has zero momentum. However, it has enormous inertia, which is different from momentum. Momentum requires motion; inertia exists even without motion.
Q35. A large force applied over a very short time interval produces:
• A small change in momentum
• No change in momentum
• A large change in momentum
• Constant momentum
Answer: A large change in momentum
The product F × Δt is called impulse, and it equals the change in momentum (Δp). A large F, even with a small Δt, can create a significant Δp. This is how a hammer drives a nail—the large force during the brief impact changes the nail’s momentum dramatically.
Q36. When an object’s velocity increases while mass remains constant, its momentum:
• Decreases
• Remains unchanged
• Increases proportionally
• Becomes zero
Answer: Increases proportionally
Momentum p = m × v is directly proportional to velocity when mass is constant. Double the velocity, double the momentum. This linear relationship is why speeding cars are so dangerous—a small increase in speed creates a proportional increase in momentum and kinetic energy.
Q37. One newton (1 N) of force is equivalent to:
• 1 kg·m/s (momentum unit)
• 1 kg·m/s² (mass times acceleration)
• 1 m/s² (acceleration unit)
• 1 kg·m² (mass times area)
Answer: 1 kg·m/s² (mass times acceleration)
From F = m × a, with m in kg and a in m/s², force has units of kg·m/s². This combination is named the newton. So 1 N = 1 kg × 1 m/s². It’s the force needed to accelerate a 1 kg mass at 1 m/s².
Q38. In the equation p = mv, the symbol ‘p’ represents:
• Power
• Pressure
• Momentum
• Potential energy
Answer: Momentum
In physics, ‘p’ is the standard symbol for linear momentum. This convention helps avoid confusion with mass (m) and velocity (v). Remember: p = momentum, which depends on both m and v.
Q39. The change in an object’s momentum (Δp) is equal to:
• Force × Time
• Mass × Acceleration
• Mass × Time
• Velocity × Time
Answer: Force × Time
This relationship, Δp = F × Δt, is called the impulse-momentum theorem. It tells us that the change in momentum equals the product of the average force and the time interval over which it acts. This is why follow-through is important in sports—longer contact time means greater momentum transfer.
Q40. Which two factors determine the magnitude of an object’s momentum?
• Mass only
• Velocity only
• Mass and velocity
• Shape and color
Answer: Mass and velocity
Momentum is the product m × v. Both factors are equally important. A tiny particle moving at near-light speed (high v, low m) can have significant momentum, as can a slow-moving ocean liner (low v, extremely high m). They combine to give the total “quantity of motion.”
Q41. According to F = ma, if force increases while mass remains constant:
• Acceleration decreases
• Acceleration remains constant
• Acceleration increases proportionally
• Acceleration becomes infinite
Answer: Acceleration increases proportionally
The equation shows a simple direct relationship: a = F/m. If m is fixed, acceleration is directly proportional to force. Push twice as hard on a shopping cart, it accelerates twice as much. This linear relationship is fundamental to predicting motion.
Q42. If a car takes longer to come to a stop during braking, the average braking force is:
• Larger
• Smaller
• Infinite
• Zero
Answer: Smaller
Stopping means changing momentum to zero: Δp is fixed. From F_avg = Δp/Δt, if the stopping time (Δt) is longer, the average force (F_avg) is smaller. This is why anti-lock brakes (ABS) pulse to maintain longer contact time and prevent skidding—they actually reduce the peak force while increasing stopping time slightly.
Q43. A high-speed object poses greater danger primarily because it carries:
• Low inertia
• Low momentum
• High momentum
• No force
Answer: High momentum
At high speeds, even moderate-mass objects gain enormous momentum (p = m × v). In a collision, this momentum must be dissipated quickly, generating tremendous forces. This is why speed limits exist and why crashes at highway speeds are so much more severe than at low speeds.
Q44. To minimize injury during an impact, the time over which stopping occurs should be:
• Increased as much as possible
• Decreased to zero
• Kept constant
• Made unpredictable
Answer: Increased as much as possible
From F = Δp/Δt, for a given momentum change (Δp), increasing the stopping time (Δt) decreases the average force (F). Airbags, crumple zones, and safety nets all work by increasing Δt to reduce F, thereby reducing the force on the human body.
Q45. If an object’s mass doubles while its velocity remains constant, its momentum:
• Remains the same
• Doubles
• Halves
• Becomes zero
Answer: Doubles
Since p = m × v, and v is constant, momentum is directly proportional to mass. Double the mass, double the momentum. A fully loaded truck moving at 50 km/h has twice the momentum of the same truck empty at 50 km/h.
Q46. Momentum is correctly classified as a vector quantity because it:
• Has only magnitude (like speed)
• Has only direction
• Has both magnitude and specific direction
• Is always constant
Answer: Has both magnitude and specific direction
Like displacement, velocity, and force, momentum requires both a size (“how much”) and a direction (“which way”) for complete description. In collision calculations, momentum conservation applies separately to each direction (x, y, z), which is only meaningful for vectors.
Q47. When an object’s acceleration is measured to be zero, the net force acting on it must be:
• At its maximum
• At its minimum
• Zero
• Infinite
Answer: Zero
From Newton’s Second Law: F_net = m × a. If a = 0, then F_net = 0 regardless of mass. This means all forces are perfectly balanced. The object could be at rest or moving with constant velocity, but either way, there’s no unbalanced force causing acceleration.
Q48. A 5 kg object experiencing an acceleration of 2 m/s² has a net force acting on it of:
• 2.5 N
• 5 N
• 10 N
• 20 N
Answer: 10 N
Using F = m × a: F = 5 kg × 2 m/s² = 10 kg·m/s² = 10 N. This means whatever forces are acting on the object (pushes, pulls, friction, etc.), their vector sum totals 10 newtons in the direction of the acceleration.
Q49. The constant ‘k’ in the general form of Newton’s Second Law (F = kma) equals 1 when:
• We use SI units consistently
• Mass is measured in pounds
• Velocity is very high
• Acceleration is decreasing
Answer: We use SI units consistently
The constant k is actually 1 by definition when we use coherent units. In the SI system, the newton is defined such that 1 N = 1 kg × 1 m/s². This makes k = 1 and gives us the simple F = ma. In other unit systems, k would have a different value.
Q50. The momentum of an object changes only when:
• No forces act on it
• Balanced forces act on it
• An unbalanced net force acts on it
• Its mass spontaneously changes
Answer: An unbalanced net force acts on it
This is Newton’s Second Law in its fundamental form: F_net = Δp/Δt. If F_net = 0 (balanced forces), then Δp = 0, meaning momentum doesn’t change. Only when there’s an unbalanced net force does momentum change over time. This is true even if mass is changing (like a rocket losing fuel).