CBSE Class 9 Science Chapter 06 How Forces Affect Motion MCQs Set 03

Multiple Choice Questions (MCQs) for Class 9 Science: Chapter 06 How Forces Affect Motion

Review structured MCQ sets for Class 9 Science Chapter 06 How Forces Affect Motion. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.

Practice Chapter 06 How Forces Affect Motion MCQs for Class 9 Science

Access the complete set of multiple-choice questions for Chapter 06 How Forces Affect Motion below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.

Question: A student pushes a 25 kg block that is initially at rest, applying a steady 55 N force while friction opposes the motion with a maximum of 50 N. What acceleration does the block gain?
A. 0.2 m s-2
B. 2.2 m s-2
C. 2.0 m s-2
D. 5.0 m s-2
Show Answer & Explanation

Answer: (A) 0.2 m s-2

Explanation:
The two forces don't cancel out here since 55 N is larger than the 50 N friction.
• Net force = 55 N minus 50 N = 5 N
• Dividing by the mass, a = F/m = 5 N / 25 kg = 0.2 m s-2
This matches the reasoning used in the chapter's worked example on pushing a stationary block.

Question: Which of the following correctly captures Newton's second law of motion as described in the chapter?
A. Acceleration is directly proportional to the net force and inversely proportional to the object's mass
B. Acceleration is directly proportional to the object's mass and inversely proportional to the net force
C. Acceleration always equals the net force, regardless of mass
D. Acceleration depends only on mass and not on the applied force
Show Answer & Explanation

Answer: (A) Acceleration is directly proportional to the net force and inversely proportional to the object's mass

Explanation:
A bigger push gives a bigger acceleration, but a heavier object resists that push more, so acceleration rises with force and falls with mass, exactly as expressed in a = F/m.

Question: In the sports car example, the velocity-time graph is a horizontal line between 5 s and 10 s. What does this segment reveal about the force acting on the car during that time?
A. No net force acts on the car since its velocity does not change
B. A constant forward force keeps pushing the car
C. A force equal to the car's weight is acting on it
D. Friction exactly cancels the car's acceleration
Show Answer & Explanation

Answer: (A) No net force acts on the car since its velocity does not change

Explanation:
A flat velocity-time line simply means the speed stays fixed, so there is no acceleration at all, and by Newton's second law that means the net force acting on the car during this interval is zero.

Question: The chapter mentions a more complete version of Newton's second law expressed using momentum. How is momentum defined there?
A. The product of an object's mass and its velocity
B. The product of an object's mass and its acceleration
C. The ratio of applied force to mass
D. The product of force and the time it acts
Show Answer & Explanation

Answer: (A) The product of an object's mass and its velocity

Explanation:
Momentum combines how much matter is moving and how fast it moves; it points in the same direction as the object's velocity.

Question: In Activity 6.4, the pulling force on the cart was kept unchanged while the cart's mass was doubled. What outcome confirmed the hypothesis linking mass and acceleration?
A. The acceleration decreased
B. The acceleration increased
C. The acceleration remained exactly the same
D. The cart stopped moving altogether
Show Answer & Explanation

Answer: (A) The acceleration decreased

Explanation:
Since force stayed constant, adding more mass made the cart harder to speed up, so the measured acceleration dropped, supporting the idea that acceleration is inversely related to mass.

Question: A ball floats motionless on the surface of a pond. Which pair of forces act on it, and how do their magnitudes compare?
A. Gravitational force pulling it down and buoyant force pushing it up, equal in magnitude
B. Friction and normal force, equal in magnitude
C. Gravitational force and normal force, unequal in magnitude
D. Buoyant force and friction, opposite but unequal
Show Answer & Explanation

Answer: (A) Gravitational force pulling it down and buoyant force pushing it up, equal in magnitude

Explanation:
Because the ball stays still rather than sinking or rising, the downward pull of gravity and the upward buoyant force from the water must be balancing each other exactly.

Question: While a weightlifter holds a loaded barbell perfectly steady overhead, without lifting or lowering it, what can be concluded about the forces acting on the barbell?
A. The forces are balanced, since the barbell has zero acceleration
B. The upward force she applies exceeds the downward gravitational pull
C. Gravity pulling the barbell down exceeds the force she applies
D. No gravitational force acts on the barbell at that moment
Show Answer & Explanation

Answer: (A) The forces are balanced, since the barbell has zero acceleration

Explanation:
A steady, unmoving barbell has constant (zero) velocity, and Newton's first law tells us this is only possible when the net force acting on it is zero.

Question: The chapter notes that a falling fruit and the Earth pull each other with an equal gravitational force, yet only the fruit is seen accelerating toward the ground. What accounts for this?
A. The Earth's mass is so enormous that its resulting acceleration is far too small to detect
B. The Earth does not actually experience any force from the fruit
C. The fruit somehow exerts a stronger force than the Earth does on it
D. Gravitational pull only affects objects lighter than a certain mass
Show Answer & Explanation

Answer: (A) The Earth's mass is so enormous that its resulting acceleration is far too small to detect

Explanation:
Since acceleration equals force divided by mass, the same force produces a huge acceleration on the light fruit but a negligible one on the massive Earth.

Question: During a tug of war, one team pulls with a noticeably greater force than the other. In which direction does the rope move?
A. Toward the team applying the larger force, with the net force equal to the difference of the two
B. Toward the weaker team, since the rope resists the stronger side
C. It remains stationary no matter how unequal the pulls are
D. Sideways, perpendicular to both pulling directions
Show Answer & Explanation

Answer: (A) Toward the team applying the larger force, with the net force equal to the difference of the two

Explanation:
When two opposing forces are unequal, they no longer cancel out completely; a leftover, or net, force remains in the direction of the stronger pull, and that is the direction the rope shifts toward.

Question: The chapter mentions that air also exerts a frictional force on a box moving through it, yet this effect is usually left out of everyday calculations. Why is that?
A. Its magnitude is typically too small to meaningfully affect the object's motion
B. Air friction always acts along the same direction as the motion
C. Air friction is generally stronger than surface friction
D. Moving air has no physical effect on solid objects
Show Answer & Explanation

Answer: (A) Its magnitude is typically too small to meaningfully affect the object's motion

Explanation:
Air resistance on a slow-moving box on a floor is real but so tiny compared to the applied force and surface friction that ignoring it barely changes the result.

Question: In Activity 6.5, a person sitting on a chair with wheels pushes a heavy table away using both hands. What happens to the chair as a consequence?
A. It rolls backward, away from the table
B. It stays completely still since only the table is being pushed
C. It rolls forward, toward the table
D. It moves sideways instead of backward or forward
Show Answer & Explanation

Answer: (A) It rolls backward, away from the table

Explanation:
Whenever the person pushes the table forward, the table pushes back on the person with an equal and opposite force, and this reaction sends the chair rolling in the opposite direction.

Question: The chapter's note on measuring force compares everyday sensitivity with laboratory precision. What range does it describe?
A. A light touch is around a millinewton, while scientists can detect forces as tiny as a yoctonewton in special experiments
B. A light touch is around a newton, while scientists can detect forces as tiny as a millinewton
C. A light touch is around a kilonewton, while scientists can detect forces as tiny as a newton
D. A light touch is around a micronewton, while scientists can detect forces as tiny as a millinewton
Show Answer & Explanation

Answer: (A) A light touch is around a millinewton, while scientists can detect forces as tiny as a yoctonewton in special experiments

Explanation:
• The chapter gives millinewtons (10^-3 N) as the rough scale of forces we can feel directly, such as a gentle touch
• It then contrasts this with far smaller forces scientists can measure in specialised setups
• That extreme sensitivity goes all the way down to yoctonewtons (10^-24 N)

Question: When two people push a stalled car in the same direction, how does the chapter say the net force on the car should be calculated?
A. By adding the magnitudes of both individual forces, since they act along the same direction
B. By subtracting the smaller force from the larger one
C. By taking only the larger of the two forces and ignoring the smaller one
D. By averaging the two applied forces
Show Answer & Explanation

Answer: (A) By adding the magnitudes of both individual forces, since they act along the same direction

Explanation:
Because both people are pushing the car the same way, their efforts combine directly rather than cancel, so the resulting net force is simply their sum, acting in that shared direction.

Question: In Example 6.3, if an object already in motion has zero net force acting on it, what will its position-time and velocity-time graphs look like?
A. Position-time graph rises as a straight line with constant slope, while velocity-time graph stays flat
B. Position-time graph stays flat, while velocity-time graph rises as a straight line
C. Both graphs are flat horizontal lines
D. Both graphs rise steadily at the same increasing rate
Show Answer & Explanation

Answer: (A) Position-time graph rises as a straight line with constant slope, while velocity-time graph stays flat

Explanation:
With no net force, the object keeps moving at constant velocity, so its position keeps changing steadily with time (a straight sloped line) while its velocity itself never changes (a flat line).

Question: The chapter mentions a situation where equal and opposite forces are applied at the two ends of an object like a handlebar or a tap. What effect do such forces produce, as distinct from ordinary balanced or unbalanced forces?
A. They cause the object to rotate rather than simply move or stay still
B. They cause the object to accelerate in a straight line
C. They cancel out completely, leaving the object unaffected
D. They cause the object to shrink in size
Show Answer & Explanation

Answer: (A) They cause the object to rotate rather than simply move or stay still

Explanation:
This case goes beyond the usual forward-backward force analysis covered earlier in the chapter. When equal and opposite forces act at opposite ends of an extended object, such as turning a tap or a handlebar, the result is turning motion, a topic the chapter says is explored further in later grades.

Question: Besides the force applied through paddling, what does the chapter note about other influences on how fast a canoe actually travels?
A. Factors like drag, water currents, the canoe's mass and rowing style also affect its speed
B. Only the paddler's strength determines the canoe's speed
C. The canoe's speed depends solely on the buoyant force from the water
D. Speed is unaffected by anything except the direction of paddling
Show Answer & Explanation

Answer: (A) Factors like drag, water currents, the canoe's mass and rowing style also affect its speed

Explanation:
The paddle-and-water force pair explains why the canoe moves forward at all, but the chapter is careful to add that real-world speed also depends on drag, currents, the boat's mass and how the rowing is done.

Question: According to the chapter's historical account, how many laws of motion did Newton present in 1687 alongside introducing the idea of inertia?
A. Three
B. Two
C. Four
D. Five
Show Answer & Explanation

Answer: (A) Three

Explanation:
Newton framed his first law using the concept of inertia and went on to present two additional laws in the same work, giving the three laws of motion that form the core of this chapter.

Question: The chapter illustrates Newton's third law using bar magnets and similarly charged balloons repelling each other. What point is this meant to demonstrate?
A. That the third law holds true for non-contact forces just as much as for contact forces like pushing or pulling
B. That magnetic and electrostatic forces are stronger than contact forces
C. That only contact forces obey Newton's third law
D. That non-contact forces do not have a reaction force at all
Show Answer & Explanation

Answer: (A) That the third law holds true for non-contact forces just as much as for contact forces like pushing or pulling

Explanation:
• Most of the chapter's third-law examples involve touching, like pushing a table or climbing a tree
• The magnet and charged-balloon illustrations extend the idea further
• They show equal and opposite forces arise even when objects never physically touch, as with magnetic or electrostatic forces

Question: In the two-boxes-connected-by-a-string example, what does the chapter call the internal force that Box 1 and Box 2 exert on each other through the string?
A. Tension
B. Normal force
C. Net force
D. Buoyant force
Show Answer & Explanation

Answer: (A) Tension

Explanation:
The string transmits a pulling force between the two boxes in opposite directions, and the chapter labels this internal force as tension, distinguishing it from the external force F pulling the whole system.

Question: The chapter gives a simple everyday reference to help you feel how strong one newton of force is. Which action produces a force close to 1 N?
A. Holding a 100 g mass steady in your palm
B. Two people pushing a stalled car together
C. Pulling a stretched spring balance to its full reading
D. Bringing down a coconut forcefully to crack it
Show Answer & Explanation

Answer: (A) Holding a 100 g mass steady in your palm

Explanation:
A 100 g mass held in the palm is pulled down by gravity with a force of roughly 1 N, so the palm must push up with about the same amount to keep it steady.

Question: While walking, what interaction between the foot and the ground actually pushes a person ahead?
A. The foot pushes the ground backward, and the ground pushes the foot forward with an equal frictional force
B. The foot pushes the ground forward, and the ground pushes the foot forward as well
C. The normal force from the ground alone carries the person ahead
D. Body weight alone tips the person forward with each step
Show Answer & Explanation

Answer: (A) The foot pushes the ground backward, and the ground pushes the foot forward with an equal frictional force

Explanation:
Every forward step relies on a backward push against the ground being answered by an equal and opposite push from the ground itself, and this reaction force is delivered through friction. Without that grip, as the chapter notes, the foot would simply slide backward instead of driving the person forward.

Question: In the worked example of a 1500 kg sports car heading east, its velocity rises steadily from rest to 10 m/s over the first 5 seconds. What force must be acting on it during this stretch?
A. 3000 N towards the east
B. 1500 N towards the east
C. 3000 N towards the west
D. 750 N towards the east
Show Answer & Explanation

Answer: (A) 3000 N towards the east

Explanation:
The acceleration works out to 2 m/s^2 over that interval, and multiplying by the car's mass of 1500 kg gives a force of 3000 N. Since the car speeds up while heading east, the force must point east as well.

Question: For quick, approximate calculations involving gravitational force, what rounded value of g does the chapter suggest using instead of 9.8 m/s^2?
A. 10 m/s^2
B. 9 m/s^2
C. 11 m/s^2
D. 9.8 m/s^2 exactly, with no rounding allowed
Show Answer & Explanation

Answer: (A) 10 m/s^2

Explanation:
9.8 m/s^2 is the standard value near Earth's surface, but the chapter mentions that 10 m/s^2 works fine as a convenient rounded number for quick estimates.

Question: What did the cart-and-pulley experiment (Activity 6.3), where the hanging load was doubled to change the pulling force, help confirm?
A. For a cart of fixed mass, a larger applied force produces a larger acceleration
B. For a cart of fixed mass, a larger applied force produces a smaller acceleration
C. Acceleration has no connection to the force applied on a cart
D. Doubling the force always exactly triples the acceleration
Show Answer & Explanation

Answer: (A) For a cart of fixed mass, a larger applied force produces a larger acceleration

Explanation:
• The cart was pulled by a thread attached to a falling cup, and increasing the mass in the cup increased the pulling force
• With the same cart mass, a stronger pull made the cart cover the same distance in less time
• Comparing the two time readings showed the acceleration had gone up along with the force, supporting the hypothesis that force and acceleration rise together for a fixed mass

Question: The chapter draws a distinction between two situations that both involve equal and opposite forces of the same magnitude. What separates a Newton's third law force pair from a pair of balanced forces?
A. A third law pair acts on two different objects and never cancels out, while balanced forces act on the same object and cancel each other
B. A third law pair acts on the same object and cancels out, while balanced forces act on two different objects
C. Both types of force pairs always act on the same object and always cancel each other
D. Both types of force pairs act on different objects, so neither type ever produces zero net force
Show Answer & Explanation

Answer: (A) A third law pair acts on two different objects and never cancels out, while balanced forces act on the same object and cancel each other

Explanation:
Third law pairs (like a paddle pushing water and water pushing the paddle) always act on separate bodies, so they can never balance each other out even though they are equal and opposite. Balanced forces, by contrast, act together on a single object, which is why their combined effect is zero net force.

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