Relative Velocity

Unspecified year 9 questions

1. Two trains, each 40 m long are travelling in opposite direction with equal velocity $20 m/s$. The time of crossing is
2. The graph shown below represent [add image]
3. The speed of a swimmer in still water is $16 m/s$. The speed of river water is $8 m/s$ and is flowing due east. If he is standing on the south bank and wiches to cross the river along the shortest path. The angle at which he should make his strokes w.r.t. north is given by
4. A train of 150 m length is going towards north direction at a speed of $10 ms^{-1}$. A parrot flies at a speed of $5 ms^{-1}$ towards south direction parallel to the railway track. The time taken by the parrot to cross the train is equal to
5. A boat takes 2 hours to travel 8 km and back in still water lake. With water velocity of $4 km h^{-1}$, the time taken for going upstream of 8 km and coming back is
6. An object has velocity $\vec{v}_{1}$ relative to the ground. An observer moving with a constant velocity $\vec{v}_{0}$ relative to the ground measures the velocity of the object to be $\vec{v}_{2}$ (relative to the observer). The magnitudes of these velocities are related by
7. Two trains are each 50 m long moving parallel towards each other at speeds $10 m/s$ and $15 m/s$ respectively. After what time will they pass each other?
8. A ship A is moving Westwards with a speed of $10 km h^{-1}$ and a ship B 100 km South of A, is moving Northwards with a speed of $10 km h^{-1}$. The time after which the distance between them becomes shortest, is
9. A bus is moving with a velocity of $10 ms^{-1}$ on a straight road. A scootorist wishes to overtake the bus in one minute. If the bus is at a distance of 1.2 km ahead, then the velocity with which he has to chase the bus is