According to Galileo's law of inertia, an object moving on a frictionless horizontal plane will:
ADecelerate and eventually stop
BContinue to move with constant velocity
CAccelerate uniformly forever
DOscillate about its starting point
Answer & Solution
Correct answer: B. Continue to move with constant velocity
1. Galileo concluded from inclined-plane experiments that motion on a frictionless horizontal plane is intermediate between acceleration (down-slope) and retardation (up-slope).
2. Without friction or any unbalanced force, the body neither speeds up nor slows down.
3. Therefore it must continue with constant velocity — the principle of inertia.
4. Newton later codified this as the First Law of Motion.
_Source: NCERT Class 11 Physics Ch 4 "Laws of Motion", §4.3 The Law of Inertia, p. 50_
Related questions
A constant force of 6 N acts for 4 s on a 2 kg body initially at rest. The kinetic energy A stone of mass 0.5 kg is whirled in a horizontal circle of radius 1 m at constant angularA car of mass 1000 kg accelerates from rest to 20 m s⁻¹ in 5 s on a level road. The net hoA man weighing 50 kg jumps off a stationary boat of mass 250 kg into water with a horizontNewton's third law states that 'action and reaction are equal and opposite'. The most accuTwo identical billiard balls strike a smooth rigid wall with equal speeds u. Ball A strikeA force F acts on a particle making an angle θ with its instantaneous velocity. The componA cricketer draws his hands back while catching a fast ball. The physical reason is that: