Newton's Laws — Set 2
Physics · न्यूटन के नियम · Questions 11–20 of 60
Which force opposes the relative motion between two surfaces in contact?
Correct Answer: B. Friction
Friction is the contact force that acts in the opposite direction of the intended or actual motion. It arises due to the microscopic irregularities present on the surfaces of objects. Friction can be reduced by using lubricants or making surfaces smoother.
A book lying on a table exerts a downward force; the table exerts an upward force called?
Correct Answer: C. Normal Force
The normal force is the perpendicular contact force exerted by a surface on an object. It balances the weight of the book to keep it in a state of equilibrium. This is a specific application of Newton's laws to static objects.
The 'recoil' of a gun after firing a bullet is an example of which law?
Correct Answer: D. Third Law
The correct answer is 'Third Law'. The gun exerts a forward force on the bullet, and the bullet exerts an equal backward force on the gun. This backward movement of the gun is known as the recoil. This phenomenon also demonstrates the conservation of linear momentum.
In which type of reference frame do Newton's laws hold true without modification?
Correct Answer: A. Inertial frame
Newton's laws are valid in inertial frames, which are frames moving at a constant velocity. In non-inertial frames, pseudo-forces must be added to account for the frame's acceleration. The Earth is generally treated as an inertial frame for most practical physics problems.
Which quantity is defined as the rate of change of momentum?
Correct Answer: D. Force
Newton's Second Law states that force is equal to the rate of change of linear momentum. This relationship provides a more general way to express the law for systems with varying mass. It shows that a larger force causes a faster change in an object's motion.
Why does a cricketer pull his hands backwards while catching a fast-moving ball?
Correct Answer: C. To increase the time of impact
Increasing the time of impact reduces the average force exerted on the hands according to the Second Law. This prevents injury by spreading the change in momentum over a longer duration. This technique is an application of the concept of impulse in sports.
What is the tendency of a moving object to continue moving in a straight line called?
Correct Answer: C. Inertia of Direction
Inertia of direction is the inability of a body to change its direction of motion by itself. An external force is required to move an object along a curved path. This is why passengers lean outward when a car takes a sharp turn.
An object of mass 5 kg is moving with an acceleration of 2 m/s². What is the net force?
Correct Answer: A. 10 N
Force is calculated by multiplying mass (5 kg) and acceleration (2 m/s²) which equals 10 Newtons. This direct calculation is the most basic application of Newton's Second Law. The direction of this force is the same as the direction of the acceleration.
Rocket propulsion is primarily based on which principle?
Correct Answer: C. Newton's Third Law
Rockets work by expelling gas downward (action), which pushes the rocket upward (reaction). This application of the Third Law allows rockets to accelerate even in the vacuum of space. It is also linked to the conservation of momentum of the expelled fuel.
A passenger in a moving train tosses a coin which falls behind him. This means the train is?
Correct Answer: D. Accelerating
If the train accelerates, the coin maintains its original slower horizontal velocity while the person moves forward. The relative motion makes the coin appear to fall behind the passenger. This scenario demonstrates how inertia behaves in an accelerating reference frame.