Jan 3, 2011

TIME AND DISTANCE
1. Speed v=s/t
where s = Total distance
t = Total time
2. s = vt
3.t=s/v
4. The relative velocity of two bodies moving at velocities u and v(u>v) in the same
direction is u – v.
5. The relative velocity of two bodies moving in opposite directions is u + v.
6. A train or a moving body of known length has to travel its own length in passing
a lamppost or a fixed body of insignificant size.
7. A train or a moving body must travel its own length plus the length of the
stationary body in question, if the train or the moving body has to pass a
stationary body i.e. a bridge, a railway platform etc.
8. Motion downstream or upstream:
Velocity of boat downstream = u + v
Velocity of boat upstream = u – v
Where ‘u’ is the velocity of the boat in still waters and ‘v’ is the
velocity of the stream.
9. If a man changes his speed in the ratio u : v, the corresponding ratio of times will
be
v : u