Relative Velocity MCQs for NEET

NEET Questions on Velocity

The velocity of moving objects with respect to other moving or stationary objects is called “relative velocity.”

The relative velocity of an observer B in the rest frame of another observer A is given by the formula:

Relative velocity of B relative to A =

\(\begin{array}{l}\vec{v_b}-\vec{v_a}\end{array} \)

If both the objects are moving in the same direction, then

\(\begin{array}{l}\vec{v_{ab}}=\vec{v_a}+\vec{v_b}\end{array} \)

If the objects are moving in the opposite direction, then

\(\begin{array}{l}\vec{v_{ab}}=\vec{v_a}-\vec{v_b}\end{array} \)

Questions with Answers

1. Two bikes travelling in the same direction move at a speed of 30 km/hr. The bikes are separated by a distance of 5 km. What would the speed of the car travelling in the opposite direction be if it meets these bikes at an interval of 4 minutes?

  1. 40 km/hr
  2. 45 km/hr
  3. 30 km/hr
  4. 15 km/hr

Answer: (b) 45 km/hr

2. On a rainy day, a girl standing on the road has to hold her umbrella at an angle of 300 with respect to the vertical to avoid getting drenched in the rain. She throws the umbrella and starts running at a speed of 10 km/hr. She notices that the raindrops are falling vertically on her head. What is the speed of the raindrops with respect to the ground?

  1. 20 km/hr
  2. 10 km/hr
  3. 30 km/hr
  4. 40 km/hr

Answer: (a) 20 km/hr

3. In the above problem, the speed of raindrops w.r.t to the moving girl is

  1. \(\begin{array}{l}\frac{10}{\sqrt{2}}\,km/hr\end{array} \)
  2. \(\begin{array}{l}\frac{5}{\sqrt{3}}\,km/hr\end{array} \)
  3. \(\begin{array}{l}10\sqrt{3}\,km/hr\end{array} \)
  4. \(\begin{array}{l}5\,km/hr\end{array} \)
\(\begin{array}{l}Answer: (c) 10\sqrt{3}\,km/hr\end{array} \)

4. A 150 m long train moves towards south at a speed of 10 m/s. A sparrow flying at a speed of 5 m/s towards north crosses the train. What is the time taken by the sparrow to cross the train?

  1. 30 s
  2. 15 s
  3. 8 s
  4. 10 s

Answer: (d) 10 s

5. A river flows east to west at a speed 5 m/min. A man capable of swimming 10 m/min in still water is standing on the south bank of the river. He wants to swim across the river in the shortest time possible. Which of the following path should he choose?

  1. Due North
  2. Due North-East
  3. Due North-East with double the speed of the river
  4. None of the above

Answer: (a) Due North

6. A person who aims to reach the exact opposite point on the bank of a stream swims at a speed of 0.5 m/s at an angle of 1200 following the direction of the water flow. What is the speed of water in the stream?

  1. 1 m/s
  2. 0.25 m/s
  3. 0.5 m/s
  4. 0.433 m/s

Answer: (b) 0.25 m/s

7. X moves at a speed of 65 km/hr while Y who is behind X moves at a speed of 80 km/hr. What is the relative velocity of Y with respect to X?

  1. 60 km/hr
  2. 80 km/hr
  3. 145 km/hr
  4. 15 km/hr

Answer: (d) 15 km/hr

8. A person who aims to reach the exact opposite point on the bank of a stream swims at a speed of 0.5 m/s at an angle of 1200 following the direction of the water flow. What is the speed of water in the stream?

  1. 1 m/s
  2. 0.5 m/s
  3. 0.25 m/s
  4. 0.433 m/s

Answer: (c) 0.25 m/s

9. A deer being preyed upon by the lion runs at a speed of 9 m/s. The lion chases the deer running at a speed of 10 m/s. If the instantaneous separation of deer from the lion is 100 m. How long would it take the lion to catch the deer?

  1. 1 second
  2. 19 seconds
  3. 90 seconds
  4. 100 seconds

Answer: (d) 100 seconds

10. A man travelling in a bus moves from west to east with a speed of 40 km/hr. He observes that the raindrops are falling vertically down. To another man standing on the ground, the rain will appear

  1. to be falling vertically down
  2. to be falling at an angle going from east to west
  3. to be falling at an angle going from west to east
  4. insufficient information is given to determine the direction of the rain

Answer: (c) to be falling at an angle going from west to east

11. A car accelerated from its initial position and then returned at the initial point, then

  1. speed is zero but velocity increases
  2. velocity is zero but speed increases
  3. both speed and velocity decrease
  4. both speed and velocity increase

Answer: (b) velocity is zero but speed increases

12. Which of these can be zero when a particle is in motion for some time?

  1. Speed
  2. Distance
  3. Displacement
  4. None of these

Answer: (c) Displacement

13. The slope of velocity-time graph for motion with uniform velocity is equal to

  1. initial velocity
  2. final velocity
  3. zero
  4. None of these

Answer: (c) zero

14. A ball is thrown vertically downward with a velocity of 20 m/s from the top of a tower. It hits the ground after some time with a velocity of 80 m/s. The height of the tower is (g =10 m/s2)

  1. 300 m
  2. 320 m
  3. 340 m
  4. 360 m

Answer: (a) 300 m

15. Two bullets are fired horizontally and simultaneously towards each other from roof tops of two buildings 100 m apart and of same height of 200 m with the same velocity of 25 m/s. When and where will the two bullets collides. (g= 10 m/s2 )

  1. They will not collide
  2. After 4s at a height of 120 m
  3. After 2s at a height of 20 m
  4. After 2s at a height 180 m

Answer: (d) After 2s at a height 180 m

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