Question

A coin at rest is dropped from the top of a tower. What is the coin's velocity after it has fallen for$5s$?
A. 49
B. 45
C. 40
D. 50

Answer 1

Hint : The velocity of an object is a function of time and is defined as the rate of change of its position concerning a frame of reference. The definition of velocity is a specification of an object's speed and direction of motion.

Complete step-by-step solution:
The concept of velocity is fundamental in kinematics, the branch of classical mechanics that describes the motion of bodies. Velocity is a physical vector quantity that requires both magnitude and direction to define. Speed is the scalar absolute value (magnitude) of velocity, and it is a coherently derived unit whose quantity is measured in the SI (metric system) as meters per second ($m/s$ or$m{{s}^{-1}}$).
"$5$ meters per second," for example, is a scalar, whereas "$5$ meters per second east" is a vector. If there is a change in speed, direction, or both, the object's velocity changes and it is said to be accelerating.
In the above example,
We know the initial velocity is zero if the object is dropped. The object is in free fall once it has lost contact with whatever held or threw it. Under these conditions, the motion is one-dimensional and has a constant g acceleration.
given data,
$u=0$
$g=9.8m/{{s}^{2}}$
$t=5s$
$v=?$
Using $v=u+gt$, we have
$v=0+9.8m/{{s}^{2}}\times 5s$
$=49m/s$
Thus, the coin's velocity after it has fallen for $5s$is$49m/s$.

Note: Relative velocity is the measurement of velocity between two objects in a single coordinate system. Because many physics systems deal with the relative motion of two or more particles, the relative velocity is fundamental in both classical and modern physics. The relative velocity in Newtonian mechanics is independent of the inertial reference frame.