Important Formulas: Motion in a Straight Line | Physics Class 11 - NEET PDF Download

 Page 1


RECTILINEAR MOTION
Average Velocity  (in an interval) :
v
av
 = v = <v>  =  
taken time Total
nt displaceme Total
 = 
t
r r
i f
?
?
Average Speed (in an interval)
Average Speed =  
taken time Total
travelled distance Total
Instantaneous Velocity (at an instant) :
inst
v
?
 = ?
?
?
?
?
?
?
?
?
?
? ? t
r
lim
0 t
?
Average acceleration (in an interval):
av
a
?
 = 
t
v
?
?
?
 =  
t
v v
i f
?
?
? ?
Instantaneous Acceleration (at an instant):
a
?
 = 
dt
v d
?
 = 
?
?
?
?
?
?
?
?
?
?
? ? t
v
lim
0 t
Graphs in Uniformly Accelerated Motion along a straight line
(a ? 0)
? x is a quadratic polynomial in terms of t. Hence x ? t graph is a
parabola.
x
i
x
 a > 0
t
0
x
i
x
a < 0
t
0
      x-t  graph
? v is a linear polynomial in terms of t. Hence v ?t graph is a straight line of
slope a.
v
u
a is positive
slope = a
t
0
v
u
a is negative
slope = a
t
0
Page 2


RECTILINEAR MOTION
Average Velocity  (in an interval) :
v
av
 = v = <v>  =  
taken time Total
nt displaceme Total
 = 
t
r r
i f
?
?
Average Speed (in an interval)
Average Speed =  
taken time Total
travelled distance Total
Instantaneous Velocity (at an instant) :
inst
v
?
 = ?
?
?
?
?
?
?
?
?
?
? ? t
r
lim
0 t
?
Average acceleration (in an interval):
av
a
?
 = 
t
v
?
?
?
 =  
t
v v
i f
?
?
? ?
Instantaneous Acceleration (at an instant):
a
?
 = 
dt
v d
?
 = 
?
?
?
?
?
?
?
?
?
?
? ? t
v
lim
0 t
Graphs in Uniformly Accelerated Motion along a straight line
(a ? 0)
? x is a quadratic polynomial in terms of t. Hence x ? t graph is a
parabola.
x
i
x
 a > 0
t
0
x
i
x
a < 0
t
0
      x-t  graph
? v is a linear polynomial in terms of t. Hence v ?t graph is a straight line of
slope a.
v
u
a is positive
slope = a
t
0
v
u
a is negative
slope = a
t
0
  v-t  graph
? a ?t graph is a horizontal line because a is constant.
a
a
positive
acceleration
t
0
a
a
negative
acceleration
0
  a-t  graph
Maxima & Minima
 
dx
dy
 = 0  &
dx
d
?
?
?
?
?
?
dx
dy
 < 0 at  maximum
and 
dx
dy
 = 0 &
dx
d
?
?
?
?
?
?
dx
dy
 > 0 at minima.
Equations of Motion (for constant acceleration)
(a) v = u + at
(b) s = ut + 
2
1
 at
2
s = vt ? 
2
1
 at
2
x
f
 = x
i
 + ut + 
2
1
 at
2
(c) v
2
 = u
2
  + 2as
(d) s = 
2
) v u ( ?
 t (e) s
n
 = u + 
2
a
 (2n ? 1)
For freely falling bodies : (u = 0)
(taking upward direction as positive)
(a) v = – gt
(b) s = –
2
1
 gt
2
s = vt ? 
2
1
 gt
2
h
f
 = h
i
 – 
2
1
 gt
2
(c) v
2
 = – 2gs
(d) s
n
 = –
2
g
 (2n ? 1)