1.
km/hr
to m/s conversion:
|
a km/hr =
|
|
a x
|
5
|
|
m/s.
|
|
18
|
2.
m/s
to km/hr conversion:
|
a m/s =
|
|
a x
|
18
|
|
km/hr.
|
|
5
|
4.
Time taken by a train of
length l metres to pass a pole or standing man or a signal
post is equal to the time taken by the train to cover l metres.
5.
Time taken by a train of
length l metres to pass a stationery object of length b metres
is the time taken by the train to cover (l + b) metres.
6.
Suppose two trains or
two objects bodies are moving in the same direction at u m/s
and v m/s, where u > v, then
their relative speed is = (u - v) m/s.
7.
Suppose two trains or
two objects bodies are moving in opposite directions at u m/s
and v m/s, then their relative speed is = (u + v)
m/s.
8.
If two trains of
length a metres and b metres are moving in
opposite directions at u m/s and v m/s, then:
|
The
time taken by the trains to cross each other =
|
(a + b)
|
sec.
|
|
(u + v)
|
9.
If two trains of
length a metres and b metres are moving in
the same direction at u m/s and v m/s, then:
|
The
time taken by the faster train to cross the slower train =
|
(a + b)
|
sec.
|
|
(u - v)
|
10.
If two trains (or
bodies) start at the same time from points A and B towards each other and after
crossing they take a and b sec in reaching B
and A respectively, then:
(A's speed) : (B's
speed) = (b : a)
PROBLEMS BASED ON TRAIN
Eg:-1
|
A train 125 m long passes a man,
running at 5 km/hr in the same direction in which the train is going, in 10
seconds. The speed of the train is:
SOLUTION:-
|
||||||||||||||||||||
|
||||||||||||||||||||
|
Eg:-2
A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, what is the length of the platform? |
SOLUTION:-
|
Speed
=
|
|
54
x
|
5
|
|
|
18
|
Length of the train = (15 x 20) m = 300 m.
Let the length of the
platform be x metres.
|
Then,
|
x + 300
|
=
15
|
|
36
|
No comments:
Post a Comment