Laws of Motion (Class 11 Physics)
Study Newtons three laws of motion and their applications to understand how objects move and interact.
TL;DR: Study Newtons three laws of motion and their applications to understand how objects move and interact.
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Study Newtons three laws of motion and their applications to understand how objects move and interact.
Laws of Motion MCQs with Answers & Explanations
Q1. What does Newtons First Law state?
- Energy is conserved
- An object at rest stays at rest unless acted upon by force ✓ (correct)
- Objects move in straight lines
- F = ma
Explanation: Newtons First Law (Law of Inertia) states that an object at rest remains at rest and an object in motion remains in motion unless acted upon by an unbalanced external force.
Q2. What is inertia?
- Acceleration of an object
- Force on an object
- Property that resists change in motion ✓ (correct)
- Energy of motion
Explanation: Inertia is the property of matter that resists changes in its state of motion. More massive objects have greater inertia.
Q3. What does Newtons Second Law state mathematically?
- v = u + at
- F = v × t
- a = v²/r
- F = m × a ✓ (correct)
Explanation: Newtons Second Law: F = ma. The net force on an object equals its mass times its acceleration. Force and acceleration are directly proportional.
Q4. If a 2 kg object experiences a force of 10 N, what is its acceleration?
- 5 m/s² ✓ (correct)
- 0.2 m/s²
- 2 m/s²
- 20 m/s²
Explanation: Using F = ma: 10 = 2 × a, therefore a = 5 m/s².
Q5. What does Newtons Third Law state?
- F = ma
- For every action, there is an equal and opposite reaction ✓ (correct)
- Objects fall due to gravity
- Force equals momentum
Explanation: Newtons Third Law states that forces always occur in action-reaction pairs. If object A exerts force on object B, then B exerts equal opposite force on A.
Q6. What is the normal force?
- Force due to gravity
- Weight of object
- Perpendicular contact force between surfaces ✓ (correct)
- Applied force
Explanation: Normal force is the perpendicular contact force exerted by a surface on an object resting on it. It prevents objects from passing through surfaces.
Q7. What is tension in a string or rope?
- Force due to friction
- Weight of object
- Compressive force
- Pulling force transmitted along string ✓ (correct)
Explanation: Tension is the pulling force transmitted through a string, rope, or cable. It acts along the length of the string.
Q8. How do you find the net force on an object?
- Vector sum of all forces ✓ (correct)
- Sum of all masses
- Largest force only
- Average of forces
Explanation: Net force is the vector sum of all forces acting on an object. Forces in the same direction add; opposite forces subtract.
Q9. What does friction force depend on?
- Only the normal force
- Normal force and coefficient of friction ✓ (correct)
- Only velocity
- Only mass
Explanation: Friction force f = μN, where μ is the coefficient of friction and N is the normal force. Friction depends on both surface properties and normal force.
Q10. What is an inertial frame of reference?
- Rotating frame
- Any frame of reference
- Frame where Newtons laws apply ✓ (correct)
- Frame with gravity
Explanation: An inertial frame is a frame of reference where Newtons laws of motion are valid. It is either at rest or moving at constant velocity.
Frequently Asked Questions
Why does a passenger lurch forward when a car suddenly brakes?
This demonstrates Newtons First Law. The passenger wants to continue moving forward due to inertia. The car decelerates but the passenger continues until friction or seat restraint acts.
What is the difference between mass and weight?
Mass is the amount of matter (constant everywhere, measured in kg). Weight is gravitational force (W = mg, varies with gravity, measured in Newtons).
More Class 11 Physics MCQs
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