Newton’s First Law Of Motion MCQ - Practice Questions with Answers

Newton’s 1st law of motion states that if the (vector) sum of all the forces acting on a particle is zero, then and only then does the particle remain unaccelerated, i.e., remains at rest or moves with constant velocity.

• If $\mathrm{F}_{\mathrm{net}}=0 \Rightarrow a_{\mathrm{net}}=0 \Rightarrow$ forces in all directions are zero, i.e,

  $$
  \sum \vec{F}_x=0, \sum \vec{F}_y=0, \sum \vec{F}_z=0
  $$
   

• Newton’s first law is also called the law of inertia.

• Newton’s laws are valid in an inertial frame of reference but are not valid in a non-inertial frame of reference.

                          Frame of reference

• A frame of reference is one in which the observer makes his observation.

• Types of frame of reference:

1. Inertial frame of reference- A frame that is at rest or moving with uniform velocity along a

                                   straight line.

                                Example- 1. Car moving with velocity v=constant

                                                 2. Lift at rest.

                          2.  A non-inertial frame of reference- a frame that is accelerated and does not have a constant velocity.

                               Example- 1. The frame travels in a straight line but speeds up or slows down.

                                               2. The frame travels along a curved path.