Final Velocities

Q. Elastic forces are not always conservative. Why

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 $v{­}_1$ towards balls 2 and 3. All collisions are assumed to be elastic. If M <m, the number of collisions between the balls will be

1. One
2. Two
3. Three
4. Four

Q. for head on collision between two colliding balls of equal raddi r, the impact parameter is equal to

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

1. $0.8\text{m/s}$
2. $0.5\text{m/s}$
3. $0.3\text{m/s}$
4. $1.2\text{m/s}$

Q. A ball P of mass 2 kg undergoes an elastic collision with another ball Q at rest. After 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?

1. 0.9 kg
2. 1.2 kg
3. 1.8 kg
4. 1.5 kg

Q. sum of three forces of equal magnitude is zero draw and fond angle between them

Q.

A large mass M moving with velocity v makes an elastic head-on collision with a small mass m at rest. What will be the expression for energy lost by mass M?

1. 

2. 

3. 

4. 

Q. what are all possible conditions for the collision of two vectors?

Q. A body of mass $m_1$ moving at a constant speed undergoes an elastic collision with a body of mass $m_2$ initially at rest., the ratio of the kinetic energies of masses $m_2$ and $m_1$ after the collision is

1. $\frac{m_1{m}_2}{(m_1-m_2{)}^2}$
2. $\frac{\sqrt{2}{m}_1{m}_2}{(m_1-m_2{)}^2}$
3. $\frac{2m_1{m}_2}{(m_1-m_2{)}^2}$
4. $\frac{4m_1{m}_2}{(m_1-m_2{)}^2}$

Q. particle A makes a perfectly elastic collision with another particle B at rest. they fly apart in opposite direction with equal speeds. If their masses are mA and mB respectively, then (a)2ma=mB (b)3mA=mB (c)4mA=mB (d)\surd3mA= m

Q. A body of mass 2m is moving in positive X axis and a body of mass m moving with 10^1/3m/s in the positive Y axis collides at the origin and moves 60 degrees along X- axis. Find the initial velocity of the first body.

Q. If collision occurs between two elastic bodies does their kinetic energy decrease during the time of collision

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

1. $9:4$
2. $4:9$
3. $2:3$
4. $3:2$

Q.

A body of mass m is accelerated uniformly from rest to a speed v in time T. The instantaneous power delivered to the body as a function of time is given by

1. 

2. 

3. 

4. 

Q. 25. For head-on collision between two colliding balls ofequal radii r, the impact parameter is equal to(1) 2r(2) Zero(3) More than 2r(4) Less than 2r

Q.

If a shell at rest explodes, then, the centre of mass of the fragments

1. moves along an elliptical path

2. moves along a parabolic path

3. remains at rest

4. moves along a straight line

Q. When a ball of significant mass moving with speed v collide with another ball of insignificant mass at rest then why is the speed of insignificant mass 2v

Q. 90.State true or false, elastic forces are not always conservative.

Q. a girl of mass 40 kg jumps with a horizontal velocity of 5 m/s on to a cart which is moving with a velocity of 4m/s. the mass of cart is 3 kg. what is the girl velocity when she is on the cart?

Q. A car weighing 1600 kg moving with a velocity of 30 m/ s retards uniformly coming to rest in 20s. Calculate the Rate of change of momentum of the car and acceleration of the car

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

1. $8\text{kg}$
2. $5\text{kg}$
3. $7\text{kg}$
4. $10\text{kg}$

Q. A stone of mass $m$ is thrown with a velocity $u$ at a block of mass $M$ which is initially at rest. The collision between the bodies is elastic. If the final velocities of the stone and the block are in the ratio $-4:1$, then what is the ratio of the mass of the stone to the mass of the block?

1. $3:2$
2. $2:3$
3. $1:1$
4. $1:9$

Q. Two perfectly elastic particles P and Q of equal mass travel along the line joining them with velocities 15 m/sec and 10 m/sec in opposite direction. After collision, the velocity of P is and that of Q is respectively (in m/sec).

1. \N
2. 5
3. 10
4. 15
5. 20

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

1. Total momentum of the system is $7{\text{kg ms}}^{-1}$.
2. Momentum of $5\text{kg}$ mass after collision is $5{\text{kg ms}}^{-1}$.
3. Velocity of $5\text{kg}$ after collision is $1\text{m/s}$.
4. Velocity of $1\text{kg}$ before collision is $2\text{m/s}$.

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 $m,\frac{m}{2},\frac{m}{2^2},...,\frac{m}{2^{n-1}}$ respectively. What is the minimum velocity which should be imparted to the first ball of mass $m$ such that this $n^{th}$ ball will complete the vertical circle ?

1. ${\left(\frac{3}{4}\right)}^{n-1}\sqrt{5gr}$
2. ${\left(\frac{4}{3}\right)}^{n-1}\sqrt{5gr}$
3. ${\left(\frac{3}{2}\right)}^{n-1}\sqrt{5gr}$
4. ${\left(\frac{2}{3}\right)}^{n-1}\sqrt{5gr}$

Q. what does it mean to say that for completely inelastic collisions, the deformations may not be relieved and the particles move together ? what is the value of final kinetic energy ? here what does the word deformations mean ?

Q. Three blocks are initially placed as shown in the figure. Block $A$ has mass $m$ and initial velocity $v$ to the right. Block $B$ with mass $m$ and block $C$ with mass $4m$ are both initially at rest. Neglect friction. All collisions are elastic. The final velocity of block $A$ is

1. $0.6v$ to the left
2. $0.4v$ to the left
3. zero
4. $0.4v$ to the right

Q. Explain conservative forces