List of top Physics Questions on Relative Velocity

A passenger sitting in a train A moving at 90 km/h observes another train B moving in the opposite direction for 8 s. If the velocity of the train B is 54 km/h, then length of train B is:
Consider an equilateral prism (refractive index \( \sqrt{2} \)). A ray of light is incident on its one surface at a certain angle \( i \). If the emergent ray is found to graze along the other surface, then the angle of refraction at the incident surface is close to
A river is flowing from west to east direction with speed of \(9\) km/hr. If a boat capable of moving at a maximum speed of \(27\) km/hr in still water, crosses the river in half a minute, while moving with maximum speed at an angle of \(150^\circ\) to direction of river flow, then the width of the river is:
Two girls are standing at the ends 'A' and 'B' of a ground where $AB = b$. The girl at 'B' starts running perpendicular to 'AB' with velocity $V_1$. The girl at 'A' starts running simultaneously with velocity $V_2$ and in shortest distance meets the other girl in time 't'. The value of 't' is ______.
Two cities X and Y are connected by a regular bus service with a bus leaving in either direction every T min. A girl is driving scooty with a speed of 60 km/h in the direction X to Y. She notices that a bus goes past her every 30 minutes in the direction of her motion, and every 10 minutes in the opposite direction. Choose the correct option for the period T of the bus service and the speed (assumed constant) of the buses.
The velocity of a swimmer in the direction of flow of river is \(10 \, \text{kmh}^{-1}\) and that against the flow of river is \(6 \, \text{kmh}^{-1}\). The velocity of the swimmer in still water in \(\text{kmh}^{-1}\) is
A spaceship moves with a velocity of 5000 m/s. What is the relativistic factor \( \gamma \) for the spaceship? (Given that \( c = 3 \times 10^8 \, \text{m/s} \))
Two objects A and B are separated horizontally by distance ' a '. Object B moves in a direction perpendicular to distance ' a ' with velocity ' \( V_1 \) '. Simultaneously object A covers shortest distance with velocity ' V ' and meets object B in time ' t '. The time ' t ' is given by
A uniform metallic wire carries a current $2 A$, when $34 V$ battery is connected across it The mass of uniform metallic wire is $892 \times 10^{-3} kg$, density is $892 \times 10^3 kg / m ^3$ and resistivity is $17 \times 10^{-8} \Omega- m$ The length of wire is :

A solid sphere of mass $1 \,kg$ rolls without slipping on a plane surface Its kinetic energy is $7 \times 10^{-3} J$. The speed of the centre of mass of the sphere is ___$cm s ^{-1}$.

A planet having mass \(9M_e\) and radius \(4R_e\), where \(M_e\) and \(R_e\) are mass and radius of earth respectively, has escape velocity in km/s given by: (Given escape velocity on earth \(V_e= 11.2 × 10^3 m/s\))
A bullet of 10 g leaves the barrel of gun with a velocity of 600 m/s. If the barrel of gun is 50 cm long and mass of gun is 3 kg, then value of impulse supplied to the gun will be :

A body of mass \( (5 \pm 0.5) \, \text{kg} \) is moving with a velocity of \( (20 \pm 0.4) \, \text{m/s} \). Its kinetic energy will be:

Two trains 'A' and 'B' of length \('l'\) and \('4l'\) are travelling into a tunnel of length 'L' in parallel tracks from opposite directions with velocities 108 km/h and 72 km/h, respectively. If train 'A' takes 35s less time than train 'B' to cross the tunnel then. length 'L' of tunnel is:
(Given L = 60 \(l\))
A fish rising vertically upward with a uniform velocity of 8 ms-1, observes that a bird is diving vertically downward towards the fish with the velocity of 12 ms-1. If the refractive index of water is \(\frac{4}{3}\) , then the actual velocity of the diving bird to pick the fish, will be _______ ms-1
Two buses of length 60 ft and 40 ft are moving parallel towards each other at speeds 15 ft/s and 10 ft/s respectively. Time taken to pass each other is:
Particle A (at origin at \(t=0\)) moves along x-axis with velocity \(1 \, m\,s^{-1}\). Particle B moves along y-axis such that \(y = t^3\) (with \(c=1 \, m\,s^{-3}\)). Find the magnitude of relative velocity of A with respect to B at \(t = 1\,s\):
A cyclist is riding a bicycle with a speed of 35 m/s from north to south. After some time rain starts falling vertically with the same speed as of the cyclist. How the cyclist will hold the umbrella?
Consider a light ray travelling in air is incident into a medium of refractive index √2n The incident angle is twice that of refracting angle. Then, the angle of incidence will be:

A swimmer wants to cross a river from point A to point B. Line AB makes an angle of 30$^\circ$ with the flow of river. Magnitude of velocity of the swimmer is same as that of the river. The angle $\theta$ with the line AB should be ________ $^\circ$, so that the swimmer reaches point B. 

 

A boat is moving from the east bank to the west bank on a south flowing river. If the speed of the boat is 4 km/h and that of the river is 3 km/h. If the width of the river is 2 km, the distance travelled by the boat is
The speed of a swimmer in still water is \(20 m/s\). The speed of river water is \(10 m/s\) and is flowing due east. If he is standing on the south bank and wishes to cross the river along the shortest path, the angle at which he should make his strokes w.r.t. north is given by:

A 2 m wide truck is moving with a uniform speed v₀ = 8m/s along a straight horizontal road. A pedestrian starts to cross the road with a uniform speed v when the truck is 4 m away from him. The minimum value of v so that he can cross the road safely is 

A boy running on a horizontal road at 8km/h finds rain falling vertically. He increases his speed to 12km/h and finds the drops make 30^∘ with the vertical. The speed of rain with respect to the road is:
Preeti reached the metro station and found that the escalator was not working. She walked up the stationary escalator in time $t_1$. On other days, if she remains stationary on the moving escalator, then the escalator takes her up in time $t_2$. The time taken by her to walk up on the moving escalator will be