Motion in straight line Flashcards
what is motion?
if the position of the object is changing with respect to time, then it is said to be in motion.
what is rest?
if the position of the object is not changing with respect to time, then it is said to be in rest.
what is the reference point
The point of intersection of these
three axes is called origin (O) and serves as the
reference point.
what is the frame of reference
The coordinates (x, y. z) of an
object describe the position of the object with
respect to this coordinate system. To measure
time, we position a clock in this system. This
coordinate system along with a clock constitutes
a frame of reference
Define:
i) 1 dimensional motion
ii 2 dimensional motion
iii dimensional motion
i) Motion in only one out of the 3 coordinates specifiying yhe positionof the object is changing with respect to time:
-freely falling body
-motion of train in astraight railyway trck
ii) motion in whcih 2 our of 3 corrdinaates specifying the position of the obj are chanign wrt time.
-motion of obj in a circle
-motion of a carrom coin
iii) motion in whcih all 3 corrdinates specifying the position of the object is chanign wrt time
-motion of roller coaster car
- motion of kite in air
What is :
Distance
Displacement
Distance is the actual path covered by the body. Distance is total length of path covered by the particle, in definite time interval.
Scalar.
Never be 0
Displacement is the shortest Distance between the initial point and final point.
Vector
Can be +ve, - ve, or 0
What is uniform motion/ non uniform
When a body covers equal distances in equal intervals of time.
Body covers unequal distances in equal intervals of time
Body covers equal distances in unequal intervals of time
when is avg velocity = average of final velocity and inital velocyt
when object is accelerated uniformly
sign convention for free fall
upward :
u= +ve
v= +ve
g= -ve
S= +ve
downward:
u= -ve
v= -ve
g= -ve
S= -ve
Discuss the motion of object under free fall
i) When an object is released very close to the earth’s surface it is accelerated downard due to the force of gravity. The magnitude of this acceleration due to gravity is taken to be g.
ii) If air resistance is neglected, the object is said to be in free fall. If the height through which the object falls is extremely less compared to the radius of the earth, the acceleration due to gravity is taken as a constant which is 9.8 m/s2. Thus free fall is a type of uniformly accelerated motion.
iii) The object is falling along the y axis, precisely the -y axis, since we choose the upward direction to be positive. Since the acceleration due to gravity is always downard, it is in the -ve direction and hence
a=-g=-9.8m/s2
iv) An object is released from rest at y=0. Then the u=0 and eqns od motion become:
v=u-gt= -9.8 t
y=ut-1/2gt2= -4.9t2
v2= u2-2gy= -19.6y
Thus velicty and distance are represented as functions of time
give the graphs of variation of distance with time, velocity with time and acceleration with time.
are distance and displacement always the same? why or why not?
The path length traversed by an object between two points is, in general, not the same
as the magnitude of displacement. The displacement depends only on the end points;
the path length (as the name implies) depends on the actual path. In one dimension,
the two quantities are equal only if the object does not change its direction during the
course of motion. In all other cases, the path length is greater than the magnitude of
displacement.
the average speed of an object is greater than or equal to the
magnitude of the average velocity over a given time interval. The two are equal only if
the path length is equal to the magnitude of displacement.
The sign of acceleration does not indicate whether the particle is speeding or not. explaon
The sign of acceleration does not tell us whether the particle’s speed is increasing or
decreasing. The sign of acceleration (as mentioned in point 3) depends on the choice
of the positive direction of the axis. For example, if the vertically upward direction is
chosen to be the positive direction of the axis, the acceleration due to gravity is
negative. If a particle is falling under gravity, this acceleration, though negative,
results in increase in speed. For a particle thrown upward, the same negative
acceleration (of gravity) results in decrease in speed.
if an object has 0 velocity at an instant that means the obj has 0 acceleration at th point. true or false
The zero velocity of a particle at any instant does not necessarily imply zero acceleration
at that instant. A particle may be momentarily at rest and yet have non-zero
acceleration. For example, a particle thrown up has zero velocity at its uppermost
point but the acceleration at that instant continues to be the acceleration due to
gravity.
differentiate between distance and displacement
distance:
distance if the total path length covered by the body in a deifinite time interval.
scalar
can never be 0 or -ve
dependent on path lenght
there are infinitely many distances between 2 point
displacement
minimum distance bet inital and final point
vector
can be 0 or -ve
independent of path length
there is only 1 displacement between 2 points
what is acceleration
it is the rate of change of velocity. ms-2
its direction is same as that of change on velocity( not velocity itself)
