KINEMATICS L6 7 RELATIVE VELOCITY imp.pptx

kinematics

1. KINEMATICS LECTURE - 6

2. Q. Two parallel rail tracks run north-south. Train A moves north with a speed of 54  km/   h, and train B moves south with a speed of 90  km/h   . What is the (a) velocity of B with respect to A ?, (b) velocity of ground with respect to B?, and (c) velocity of a monkey running on the roof of the train A against its motion (with a velocity of 18 km h−1 with respect to the train A) as observed by a man standing on the ground ?

3. Q. Two trains 120 m and 80 m in length are running in opposite directions with velocities 42 km/h and 30 km/h respectively. In what time will they completely cross each other?

4. Q. A jet airplane travelling at the speed of 500 kmh −1 ejects its products of combustion at the speed of 1500 kmh −1 relative to the jet plane. Find the speed of the products of combustion with respect to an observer on the ground.

5. Q. Two trains A and B of length 400m each are moving on two parallel tracks with a uniform speed of 72kmh−1 in the same direction, with A ahead of B . The driver of B decides to overtake A and accelerates by 1ms−2 . If after 50s , the guard of B  just brushes past the driver of  A, what is the original distance between them.  

6. Q. Two towns A and B are connected by a regular bus service with a bus leaving in either direction every T minute. A man cycling with a speed of 20 kmh −1 in the direction A to B notices that a bus goes past him every 18 in the direction of his motion, and every 6 min in the opposite direction. What is the period T of the bus service and with what speed (assumed constant) do the buses ply on the road?

7. Q. A 150 m long train is moving to north at a speed of 10 m/s. A parrot flying towards south with a speed of 5 m/s crosses the train. The time taken by the parrot the cross to train would be (a) 5 s (b) 10 s (c) 15 s (d) 30 s

8. Q. Two trains, each 50m long are travelling in opposite direction with velocity 10m/s−1 and 15m/s−1. The time of crossing is : (a) 2 s (b) 4 s (c) 8 s (d) 16 s

9. Q. Tom and Dick are running forward with the same speed. They are throwing a rubber ball to each other at a constant speed v as seen by the thrower. According to Sam who is standing on the ground the speed of the ball is (a) Same as v (b) greater than v (c) less than v (d) none of these.

10. Q. Driver of a train travelling at 115 km/ hr sees on a same track, 100 m infront of him, a slow train travelling in the same direction at 25 km/ hr . The least retardation that must be applied to faster train to avoid a collision is ( a) 3.125  m/s2 (b) 3.5 m/s2 ( c) 2.75 m/s2 ( d) 3.0 m/s2

11. Q. A police jeep is chasing with velocity of 45 km / h , a thief in another jeep moving with velocity 153 km / h . Police fires a bullet with muzzle velocity of 180 m / s . The velocity with which it will strike the car of the thief, is: (a) 27 m/s ( b) 150 m/s ( c) 250 m/s ( d) 450 m/s