Newton's Laws — Set 4
Physics · न्यूटन के नियम · Questions 31–40 of 60
What happens to a body if the resultant force acting on it is not zero?
Correct Answer: B. It must accelerate
The correct answer is 'It must accelerate'. A non-zero resultant force always causes an object to change its velocity, which is called acceleration. This is the core principle of the Second Law of Motion. The direction of acceleration will always be the same as the direction of the net force.
The concept of 'Impulse' is mathematically defined as?
Correct Answer: B. Force × Time
Impulse is the product of the average force and the time interval for which it acts. It is equal to the total change in momentum of the object. High-impulse events like collisions usually involve very large forces over very short times.
When a carpet is beaten with a stick, dust particles come out because of?
Correct Answer: B. Inertia of Rest
Beating the carpet sets it into sudden motion, while the dust particles tend to stay at rest. Due to this inertia, the particles detach from the fibers and fall away. This serves as a common practical demonstration of the First Law.
In the absence of air resistance, which falls faster: a feather or a hammer?
Correct Answer: A. Both fall at the same rate
In a vacuum, gravity accelerates all objects at the same rate regardless of their mass. This was famously demonstrated by Galileo and later by astronauts on the Moon. Air resistance is the only factor that causes a feather to fall slower on Earth.
What is the unit of momentum in the SI system?
Correct Answer: A. kg m/s
Since momentum is mass times velocity, its unit is the product of kg and m/s. It describes how difficult it is to stop a moving object. This unit is consistent with the Newton-second which is used for impulse.
Which law is known as the 'Real Law of Motion' because the others can be derived from it?
Correct Answer: B. Second Law
The Second Law is considered the primary law because it provides the mathematical basis for motion. The First Law is a special case of the Second Law where the net force is zero. It allows for the calculation of specific values for force, mass, and acceleration.
If an object is moving at a constant speed in a straight line, the net force is?
Correct Answer: A. Zero
Constant speed in a straight line means there is no acceleration. According to F = ma, if acceleration is zero, the net force must also be zero. This condition is known as dynamic equilibrium in physics.
The working of a jet engine is an application of?
Correct Answer: A. Third Law
Jet engines expel exhaust gases backward at high speeds to generate a forward thrust. This reaction force pushes the aircraft forward according to Newton's Third Law. It is the same basic principle used in rocket engines and balloon propulsion.
Which of the following laws explains why we use seat belts in cars?
Correct Answer: C. First Law
The First Law explains that a passenger will continue moving forward if a car stops suddenly. Seat belts provide the external force needed to change this state of motion and prevent injury. They effectively overcome the passenger's inertia of motion during an accident.
What is the relationship between Force (F) and Acceleration (a) for a constant mass?
Correct Answer: B. F ∝ a
Newton's Second Law states that the acceleration of an object is directly proportional to the net force. If you double the force on a fixed mass, the acceleration will also double. This linear relationship is a fundamental concept in classical mechanics.