An object may appear to be moving for one person and stationary for some other. For the passengers in a
moving bus, the roadside trees appear to be moving backwards. A person standing on the road–side perceives
the bus along with the passengers as moving. However, a passenger inside the bus sees his fellow passengers
to be at rest.
Most motions are complex. Some objects may move in a straight line, others may take a circular path. Some
may rotate and a few others may vibrate. There may be situations involving a combination of these.
(a) Can any object be at absolute rest? [1]
(b) Is displacement a scalar quantity? [1]
(c) Define oscillatory motion. [1]
(d) Define mechanics.
Answers
Answer:
Explanation:
a) Motion is relative and no object in this universe is at absolute rest. Someone sitting on a sofa in his house is still in motion with respect to an alien on an other planet. This is because the planet earth is not only orbiting sun but is also spinning at its axis. Similarly all planetary and interstellar bodies are in the state of perpetual motion. So something can be relatively at rest but no absolutely at rest.
b) Displacement is not a scalar quantity as it requires direction along with magnitude to define it. For example Jack travelled 12 km to the north, is the displacement of Jack and displacement is vector.
c) The to and fro motion of a body about a fixed point, called the mean point is known as oscillatory motion. The body goes from one extreme position to another by making a pit stop at the mean position. For example motion of a pendulum.
d) Mechanics is a branch of physics which deals with the motion of macroscopic objects. It deals with the forces applied on the bodies and displacements or distances they cover.