# Final Velocities

## Trending Questions

**Q.**

Two particles have masses of $m$ and $4m$ and their kinetic energies are in the ratio of $2:1$. What is the ratio of their linear momenta?

$\frac{1}{2}$

$\frac{1}{\sqrt{2}}$

$\frac{1}{4}$

None of these

**Q.**Two particles of masses m1 & m2 and velocities u1 and (αu1)(α≠0) make an elastic head on collision. If the initial kinetic energies of the two particles are equal and m1 comes to rest after collision, then

- m2m1=9+2√2
- m2m1=3−2√2
- m1m2=3−2√2
- m1m2=9+√2

**Q.**A mass m1 moving with initial velocity u strikes head on to another mass m2 kept at rest as shown in figure. After collision if |v1|<|u|, then

- m1>m2
- m1<m2
- m1=m2
- There is no relation between m1 and m2

**Q.**Block A with a kinetic energy of 500 J collides with another block B of mass 10 kg initially kept at rest. Assuming that the collision is perfectly elastic, what is the final speed of the block B?

- 100 m/s
- 0 m/s
- 10 m/s
- 5 m/s

**Q.**A point mass of 1 kg collides elastically with a stationary point mass of 5 kg. After their collision, the 1 kg mass reverses its direction and moves with a speed of 2 m/s. Which of the following statements is (are) correct for the system of two masses ?

- Total momentum of the system is 7 kg ms−1.
- Momentum of 5 kg mass after collision is 5 kg ms−1.
- Velocity of 5 kg after collision is 1 m/s.
- Velocity of 1 kg before collision is 2 m/s.

**Q.**A ball of mass 1 kg is thrown with a velocity of 6 m/s at a stone of unknown mass initially at rest. If the velocity of the stone after the elastic collision with the ball is 1.5 m/s, what is the mass of the stone?

- 8 kg
- 5 kg
- 7 kg
- 10 kg

**Q.**A heavy steel ball of mass greater than 1 kg moving with a speed of 2 m sec−1collides head on with a stationary ping-pong ball of mass less than 0.1 gm. The collision is elastic. After the collision the ping-pong ball moves approximately with speed of

- 2 m/s
- 4 m/s
- 2×104m/s
- 2×103m/s

**Q.**On a frictionless surface, a block of mass M moving at speed υ collides elastically with another block of same mass M which is initially at rest. After collision the first block moves at an angle θ to its initial direction and has a speed υ3. The second block's speed after the collision is

- √32υ
- 2√23υ

34υ

3√2υ

**Q.**There are 100 identical blocks equally spaced on a frictionless track as shown in the figure. Initially all the blocks are at rest. Block (1) is pushed with velocity v towards block 2. If each of the collisions is elastic, then the velocity of the final 100th block is

- v99
- v100
- v
- zero

**Q.**A rifle man, who together with his rifle has a mass of 100 kg, stands on a smooth surface and fires 10 shots horizontally. Each bullet has a mass 10 g and a muzzle velocity of 800 m/s. What velocity does the rifle man acquire at the end of 10 shots?

- 0.8 m/s
- 0.5 m/s
- 0.3 m/s
- 1.2 m/s

**Q.**

A body of mass 1 kg makes an elastic collision with another body at rest and continues to move in the original direction after collision with a velocity equal to 14 of its original velocity. The mass of the second body is

25kg

35kg

32kg

23kg

**Q.**Balls of masses 4 kg and 10 kg are moving towards each other with speeds 6 m/s and 3 m/s respectively on a frictionless surface. After collision, the 4 kg ball is observed to return back (towards left) with speed 2 m/s. Find the velocity of 10 kg ball after collision.

- 2 m/s
- 0.2 m/s
- 9 m/s
- 1 m/s

**Q.**A ball P of mass 2 kg undergoes an elastic collision with another ball Q initially kept at rest. After the collision, ball P continues to move in its original direction with a speed one-fourth of its original speed. What is the mass of ball Q?

- 0.9 kg
- 1.2 kg
- 1.5 kg
- 1.8 kg

**Q.**Ball A of mass 10 kg moving with a velocity 6 m/s, collides with ball B of mass 50 kg which is at rest. What is the ratio of the kinetic energies of the ball A before and after the elastic collision?

- 9:4
- 4:9
- 2:3
- 3:2

**Q.**A body of mass m1 moving at a constant speed undergoes an elastic collision with a body of mass m2 initially at rest., the ratio of the kinetic energies of masses m2 and m1 after the collision is

- m1m2(m1−m2)2
- √2m1m2(m1−m2)2
- 2m1m2(m1−m2)2
- 4m1m2(m1−m2)2

**Q.**Two spheres are placed in a horizontal plane with kinetic energies (KE)A=8 J and (KE)B=18 J as shown in figure. If both the spheres collide elastically, find the speed of both the spheres after collision. Both the spheres have the same mass m=1 kg.

- VA=6 m/s VB=4 m/s
- VA=4 m/s VB=6 m/s
- VA=3 m/s VB=2 m/s
- VA=2 m/s VB=3 m/s

**Q.**Three objects A, B and C are kept in a straight line on a frictionless horizontal surface. These have masses m, 2m and m respectively. The object A moves towards B with a speed of 9 m/s and makes an elastic collision with it. Thereafter, B makes completely inelastic collision with C. All motions occur on the same straight line. Find the final speed (in m/s) of object C.

**Q.**Two spheres are placed in a horizontal plane with kinetic energies (KE)A=8 J and (KE)B=18 J as shown in figure. If both the spheres collide elastically, find the speed of both the spheres after collision. Both the spheres have the same mass m=1 kg.

- VA=6 m/s VB=4 m/s
- VA=4 m/s VB=6 m/s
- VA=3 m/s VB=2 m/s
- VA=2 m/s VB=3 m/s

**Q.**n elastic balls are placed at rest on a smooth horizontal plane which is circular at the ends with radius r as shown in the figure. The masses of the balls are m, m2, m22, ..., m2n−1 respectively. What is the minimum velocity which should be imparted to the first ball of mass m such that this nth ball will complete the vertical circle ?

- (34)n−1√5gr
- (43)n−1√5gr
- (32)n−1√5gr
- (23)n−1√5gr

**Q.**Two balls marked 1 and 2 of the same mass m and a third ball marked 3 of mass M are arranged over a smooth horizontal surface as shown in Fig. Ball 1 moves with a velocity v1 towards balls 2 and 3. All collisions are assumed to be elastic. If M <m, the number of collisions between the balls will be

- One
- Two
- Three
- Four