Describing Motion Around Us

20 Practice flashcards in Question and Answer style covering the key concepts from Rakshak Sir's physics lectures on motion, including kinematics formulas, graphing, and definitions.

What is the definition of linear motion according to the lecture notes?

When an object moves in a straight line, its motion is called linear motion.

How is a reference point used to describe the position of an object?

To describe the position of an object, a fixed point must be specified as the reference point, and the position is described with respect to that point.

Under what condition is an object said to be in motion?

An object is in motion if its position with respect to the reference point changes with time.

How is distance travelled defined?

Distance travelled is the total path length covered by an object.

What is displacement in the context of motion?

Displacement is the net change in the position of an object between two given instants of time, representing the shortest distance measured from the initial to the final position.

Compare the nature of distance and displacement in terms of quantities.

Distance is a scalar quantity, while displacement is a vector quantity.

What is the result of displacement for an object completing one round of a circular path?

The displacement is $0$.

What is the formula for average speed?

$$\text{Average Speed} = \frac{\text{Total Distance Travelled}}{\text{Total Time Taken}}$$

What is the formula for average velocity according to Lecture 02?

$$\text{Average Velocity} = \frac{\text{Displacement}}{\text{Total Time Taken}}$$

Define uniform motion.

Uniform motion occurs if an object moving in a straight line travels equal distances in equal intervals of time for all possible choices of time intervals.

Define average acceleration and provide its formula.

Average acceleration is the rate of change of velocity, calculated as $a = \frac{v-u}{t}$, where $u$ is initial velocity, $v$ is final velocity, and $t$ is time taken.

What is retardation or deceleration?

It is negative acceleration that occurs when velocity decreases with time ($a < 0$).

According to the transcript, what are the three cases where velocity changes?

Velocity changes because of (1) a change in speed, (2) a change in direction, or (3) a change in both speed and direction.

What does the slope of a position-time ($x-t$) graph represent?

The slope of a position-time graph represents velocity, calculated as $v = \frac{\triangle x}{\triangle t}$.

What does the area under a velocity-time ($v-t$) graph provide?

The area under a velocity-time graph gives the displacement.

What are the three equations of motion valid for uniformly accelerated motion?

1) $v = u + at$; 2) $s = ut + \frac{1}{2}at^{2}$; 3) $v^{2} = u^{2} + 2as$

In the NCERT Example 4.1 (Postmen Problem), in how many days will the postmen meet if they start 210 yojanas apart, traveling 9 yojanas and 5 yojanas per day respectively?

$15$ days.

Define Uniform Circular Motion (UCM).

When an object moves in a circular path with constant speed.

What is the direction of velocity in Uniform Circular Motion?

The velocity is always tangential to the circular path.

What is the formula for linear speed ($v$) in a circular path with radius $r$ and time period $T$?

v = \frac{2\times \text{\pi} \times r}{T}