Entrance Based Objective Question for Class 11

 

Here is a detailed blog post on "Force (Entrance Based Objective Question for Class 11)". In the present post, we start from the fundamentals of force and then we present 50 multiple‐choice questions (MCQs) with explanations. The MCQs that are given in this file are of following topics Newton’ s laws of motion Type of forces Equilibrium Friction And much more. Go through the explanation, try the questions and check the explanation to strengthen your hold on the course.

Force is one of the most fundamental concepts in physics. In everyday language, force is often associated with a “push” or a “pull.” In physics, however, force is a vector quantity (meaning it has both magnitude and direction) and is defined as the interaction that causes an object to accelerate according to Newton’s laws of motion.

Key points to remember:
• The SI unit of force is the Newton (N).
• Newton’s First Law (Law of Inertia) states that an object at rest remains at rest or continues in uniform motion unless acted upon by a net external force.
• Newton’s Second Law gives the relationship F = ma (where F is net force, m is mass, and a is acceleration).
• Newton’s Third Law tells us that every action has an equal and opposite reaction.
• Forces can be contact forces (like friction, tension, and normal force) or non-contact forces (like gravitational, magnetic, or electrostatic force).

1.    Which of the following is the SI unit of force?
A) Joule B) Watt C) Newton D) Pascal
• Explanation: The SI unit of force is the Newton (N).

2.    Which law of motion is known as the law of inertia?
A) Newton’s First Law B) Newton’s Second Law C) Newton’s Third Law D) Hooke’s Law
• Explanation: Newton’s First Law states that an object will remain at rest or move at a constant velocity unless acted upon by a net external force.

3.    Newton’s Second Law of Motion is best expressed by the equation:
A) F = mv B) F = ma C) F = m/v D) F = m + a
• Explanation: Newton’s Second Law is given by F = ma, relating net force, mass, and acceleration.

4.    According to Newton’s Third Law, when you push against a wall, the wall pushes back with:
A) A smaller force B) The same force C) No force D) A variable force
• Explanation: Newton’s Third Law states that every force has an equal and opposite reaction.

5.    If the net force acting on an object is zero, the object will:
A) Accelerate B) Remain at rest or move with constant velocity C) Change direction D) Increase its mass
• Explanation: When net force is zero, an object is in equilibrium, meaning no acceleration occurs.

6.    A force that acts through direct contact with an object is called a:
A) Non-contact force B) Gravitational force C) Contact force D) Magnetic force
• Explanation: Examples include friction, tension, and normal force, which require physical contact.

7.    Which of the following forces is an example of a non-contact force?
A) Friction B) Tension C) Normal D) Gravitational
• Explanation: Gravitational force acts at a distance without direct contact.

8.    What happens to an object’s acceleration if the applied net force is doubled while the mass remains unchanged?
A) It halves B) It doubles C) It remains same D) It quadruples
• Explanation: According to F = ma, doubling F doubles a if mass stays constant.

9.    An object of mass 4 kg experiences an acceleration of 5 m/s². What is the magnitude of the net force on the object?
A) 9 N B) 20 N C) 25 N D) 45 N
• Explanation: F = ma = 4 × 5 = 20 N.

10. Which type of friction acts when an object is in motion relative to a surface?
A) Static friction B) Rolling friction C) Kinetic friction D) Fluid friction
• Explanation: Kinetic friction occurs when there is relative motion between surfaces.

11. Static friction is:
A) Always greater than kinetic friction B) Always less than kinetic friction C) Equal to kinetic friction D) Irrelevant in motion
• Explanation: Generally, static friction (preventing motion) is higher than kinetic friction (during motion).

12. When an object is in equilibrium, the sum of forces acting on it is:
A) Positive B) Negative C) Zero D) Undefined
• Explanation: Equilibrium implies the net force is zero.

13. Which of the following best describes weight?
A) A measure of mass B) A measure of gravitational force C) A type of friction D) A scalar quantity
• Explanation: Weight is the gravitational force acting on an object and is a vector.

14. The weight of an object is given by:
A) mg (mass times gravitational acceleration) B) m/g C) m + g D) m - g
• Explanation: Weight = mg, where g is the acceleration due to gravity.

15. In free-fall (neglecting air resistance), all objects fall with the same acceleration because:
A) Their masses are equal B) Gravitational force is the same C) The acceleration due to gravity is constant D) Air resistance cancels out differences
• Explanation: All objects accelerate at g (approximately 9.8 m/s²) near Earth’s surface regardless of mass.

16. If two forces of equal magnitude act on an object in opposite directions, the net force is:
A) Zero B) Sum of the forces C) Difference of the forces D) Undefined
• Explanation: Equal and opposite forces cancel each other resulting in zero net force.

17. What is the effect of friction on moving objects?
A) It increases their speed B) It opposes their motion C) It changes their mass D) It acts only when objects are at rest
• Explanation: Friction opposes the relative motion between surfaces.

18. Which of the following is true about centripetal force?
A) It pushes an object outward B) It is required for circular motion C) It acts along the tangent to a circle D) It is a fictitious force
• Explanation: Centripetal force acts toward the center of the circle, keeping an object in circular motion.

19. A net force directed to the right on a stationary object will cause the object to:
A) Remain stationary B) Accelerate to the right C) Accelerate to the left D) Change direction randomly
• Explanation: The object will begin accelerating in the direction of the net force.

20. The deformation (stretching or compressing) of an object when a force is applied is described by:
A) Elasticity B) Inertia C) Viscosity D) Plasticity
• Explanation: Elasticity describes how materials return to their original shape after deformation.

21. Hooke’s Law is applicable to:
A) Perfectly plastic materials B) Elastic materials C) Inelastic collisions D) Fluids
• Explanation: Hooke’s Law (F = kx) holds for materials that obey elastic behavior.

22. In Hooke’s Law, “k” stands for:
A) Curvature B) Spring constant C) Kinetic energy D) Mass constant
• Explanation: “k” is the spring constant, reflecting the stiffness of the spring.

23. If a spring with k = 50 N/m is stretched 0.2 m from its natural length, the restoring force is:
A) 5 N B) 10 N C) 25 N D) 100 N
• Explanation: F = kx = 50 × 0.2 = 10 N.

24. Which force is responsible for keeping planets in orbit around the sun?
A) Magnetic force B) Nuclear force C) Gravitational force D) Elastic force
• Explanation: Gravitational force provides the centripetal force that keeps planets in orbit.

25. The frictional force that opposes the rotation of a wheel is called:
A) Static friction B) Rolling friction C) Kinetic friction D) Fluid friction
• Explanation: Rolling friction resists motion when an object rolls over a surface.

26. In the absence of friction, an object sliding on a horizontal surface will:
A) Eventually stop B) Move with constant velocity C) Accelerate indefinitely D) Move erratically
• Explanation: Without friction, an object continues in motion with constant velocity per Newton’s First Law.

27. Which factor does NOT affect the magnitude of frictional force?
A) Nature of the surfaces B) Normal force C) Surface area of contact D) Coefficient of friction
• Explanation: Although surface area might seem important, for many cases the frictional force is independent of the contact area and depends mainly on the normal force and the coefficient of friction.

28. An unbalanced force acting on an object:
A) Leaves the object in equilibrium B) Causes acceleration C) Reduces its mass D) Has no effect on motion
• Explanation: An unbalanced force changes the state of motion, causing acceleration.

29. When an object moves in a circle at constant speed, it is accelerating because:
A) Its speed increases B) Its direction of motion changes C) Its mass increases D) It experiences friction only
• Explanation: The change in direction of the velocity vector means there is centripetal acceleration.

30. The net force acting on an object undergoing uniform circular motion is directed:
A) Tangentially B) Radially outward C) Radially inward D) Opposite to the velocity
• Explanation: The net (centripetal) force is directed inward toward the circle’s center.

31. When two objects collide and exert forces on each other, the forces experienced are:
A) Unequal B) Equal in magnitude and opposite in direction C) Only gravitational D) Dependent on their speed only
• Explanation: Newton’s Third Law applies; they are equal and opposite.

32. In a tug-of-war where both teams pull with equal force, the rope remains:
A) In motion B) Stationary C) Accelerating D) Unpredictable
• Explanation: Equal forces on both sides produce zero net force, keeping the rope stationary.

33. Which of the following is NOT a vector quantity?
A) Force B) Velocity C) Acceleration D) Mass
• Explanation: Mass is a scalar; it has magnitude only, no direction.

34. The impulse delivered to an object is equal to:
A) The change in its velocity B) The change in its momentum C) Its weight multiplied by time D) The work done on the object
• Explanation: Impulse equals the change in momentum (Impulse = FΔt).

35. The unit of impulse is:
A) Newton B) Joule C) Newton-second D) Pascal
• Explanation: Since impulse has dimensions of force multiplied by time, its unit is N·s.

36. For an object of constant mass, an increase in net force will result in:
A) A decrease in acceleration B) No change in acceleration C) An increase in acceleration D) A change in mass
• Explanation: F = ma implies acceleration increases with net force if mass is constant.

37. Which scenario best illustrates balanced forces?
A) A car accelerating on a highway B) A book lying at rest on a table C) A ball thrown upwards D) A rocket launching
• Explanation: The book on the table is in equilibrium (balanced gravitational and normal forces).

38. When an object is thrown upwards, the net force acting on it (ignoring air resistance) is:
A) Upward B) Downward C) Zero D) Alternating
• Explanation: Gravity always acts downward regardless of the initial upward motion.

39. In the equation F = ma, if mass is doubled while force remains constant, acceleration will:
A) Double B) Halve C) Remain the same D) Quadruple
• Explanation: Acceleration is inversely proportional to mass; doubling mass halves acceleration.

40. What is the net force on an object if two forces of 15 N and 10 N act in the same direction and one force of 5 N acts in the opposite direction?
A) 20 N B) 15 N C) 10 N D) 5 N
• Explanation: Net force = 15 + 10 − 5 = 20 N in the direction of the larger force sum.

41. The term “resultant force” refers to:
A) The smallest force in a system B) The vector sum of all forces acting on an object C) The friction only D) A scalar addition of forces
• Explanation: Resultant force is determined by vector addition of all individual forces.

42. An increase in the coefficient of friction between two surfaces will generally cause:
A) Lower frictional force B) Higher frictional force C) No change in friction D) A decrease in normal force
• Explanation: A higher coefficient increases the frictional force as f = μN.

43. When a force is applied at an angle to the horizontal, the horizontal component is given by:
A) F sin θ B) F cos θ C) F tan θ D) F/θ
• Explanation: The horizontal component equals F cos θ, where θ is the angle with the horizontal.

44. For a fixed force applied at an angle, as the angle increases from 0° to 90°, the horizontal component of the force:
A) Increases B) Decreases C) Remains constant D) First increases then decreases
• Explanation: The horizontal component (F cos θ) decreases as θ increases.

45. Which of the following does NOT affect the net force on an object?
A) Magnitude of individual forces B) Directions of forces C) Time over which forces act D) Relative angles between forces
• Explanation: The net force is determined by the instantaneous vector sum of forces; time isn’t directly a factor unless impulse is considered.

46. In uniform linear motion with no acceleration, how do the applied forces compare to the opposing forces?
A) Applied forces are greater B) Opposing forces are greater C) Both are equal D) Opposing forces are zero
• Explanation: In uniform motion, forces are balanced, meaning applied and opposing forces are equal.

47. Which scenario demonstrates an object in static equilibrium?
A) A car braking B) A satellite orbiting Earth C) A hanging picture frame supported by a nail D) A ball rolling down a hill
• Explanation: In static equilibrium, as with a hanging picture frame, all forces balance so that the net force is zero.

48. In the context of forces, the term “net force” means:
A) The largest individual force acting on an object B) The difference between upward and downward forces C) The sum of all forces taking into account their directions D) Only the frictional forces
• Explanation: Net force is the vector sum of all individual forces acting on the object.

49. When an object is subject to a varying force over time, the impulse is equal to:
A) Maximum force multiplied by time B) Average force multiplied by time interval C) The sum of distances traveled D) The product of mass and velocity
• Explanation: For a variable force, impulse can be approximated by (average force × time interval) or calculated using integration.

50. A student applies a force that increases gradually on a cart. Initially, the cart does not move because static friction is greater than the applied force. This is an example of:
A) Newton’s Second Law B) Overcoming inertia C) The difference between static and kinetic friction D) Conservation of momentum
• Explanation: This scenario illustrates the difference between static friction (which must first be overcome) and kinetic friction.

Happy Learning and good luck for your entrance exam