PHYSICS XI Ch#3 Quiz 1

Perpetual meaning Permanent (دائمی).

As rest and motion are always relative so every thing in the world is always in motion w.r.t its sorroundings.

As the velocity being vector depends upon both magnitude and direction. If any of them changes then velocity changes. Therfore when a body is moving in circle then its direction changes continously so its velocity remains changing at every point during circular motion.

Acceleration is defined as "rate of change of velocity".

Therefore the direction of acceleration also depends upon change in velocity.

If the slope of velocity-time graph is decreasing with time, then it means that velocity is decreasing with time which shows that acceleration will negative. It may be uniform or variable. Given diagram shows the uniform negative acceleration.

When body falls downward then its speed goes on increasing, therefore the acceleration due to gravity will positive.

Inertial frames are not accelerated and non-inertial frames are accelerated fremes. The Earth is in an orbit, so it is constantly accelerated towards the Sun, so it's not an inertial frame.

Newton's first law states that "if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force".

Its means that force is the quantity required to stop or move the object which is defined by 1st law of motion.

 here "v" denotes the final velocity.

Newton's second law of motion can be stated as follows: "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object".