Collision of two rigid bodies - class-XI

Physics problems on collisions, coefficient of restitution, impulse, and momentum conservation in rigid bodies

20 Questions Published

Questions

Question 1 Multiple Choice (Single Answer)

A uniform rod AB of mass $3m$ and length $2l$ is lying at rest on a smooth horizontal table with a smooth vertical axis through the end $A$ . A particle of mass $2m$ moves with speed $2u$ across the table and strikes the rod at its mid point $C$. If the impact is perfectly elastic , then find the speed of the particle after impact if it strikes the rod normally 

  1. $\dfrac{7u}{3}$
  2. $\dfrac{2u}{3}$
  3. $\dfrac{u}{3}$
  4. $\dfrac{4u}{3}$
Question 2 Multiple Choice (Single Answer)

A body falls from height 20 m.If coefficient of restitution 1/2. The time interval between starting point and second bounce is $\left( {g = 10;m{s^{ - 2}}} \right)$

  1. 1 s
  2. 2 s
  3. 3 s
  4. 4 s
Question 3 Multiple Choice (Single Answer)

A disc of mass $100g$ and radius $10cm$ has a projection on its circumference. The mass of projection is negligible. A $20g$ bit of putty moving tangential to the disc with a velocity of $5m{s}^{-1}$ strikes the projection and sticks to it. The angular velocity of disc is

  1. $14.29rad{s}^{-1}$
  2. $17.3rad{s}^{-1}$
  3. $12.4rad{s}^{-1}$
  4. $9.82rad{s}^{-1}$
Question 4 Multiple Choice (Single Answer)

Two spheres $A$ and $B$ of masses $m _1$ and $m _2$ respectively collide. $A$ is at rest initially and $B$ is moving with velocity $v$ along x-axis. After collision $B$ has a velocity $\cfrac{v}{2}$ in a direction perpendicular to the original direction. The mass $A$ moves after collision in the direction

  1. Same as that of $B$
  2. Opposite to that of $B$
  3. $\theta=\tan^{-1}{(1/2)}$ to the x-axis
  4. $\theta=\tan^{-1}{(-1/2)}$ to the x-axis
Question 5 Multiple Choice (Single Answer)

A rod of length on two metal pads of same height from a height $h$. The coefficients of restitution of the metal pads are ${e} _{1}$ and ${e} _{2}$ (${e} _{1}> {e} _{2}$). The angular velocity of the rod after it recoils is

  1. $\cfrac { { e } _{ 1 } }{ { e } _{ 2 } } l\sqrt { 2gh } $
  2. $\cfrac { { e } _{ 1 }-{ e } _{ 2 } }{ l } \sqrt { 2gh } $
  3. $\cfrac { { e } _{ 1 }+1 }{ { e } _{ 2 }+1 } \sqrt { 2gh } $
  4. $\cfrac { { e } _{ 1 }+1 }{ { e } _{ 2 }-1 } \sqrt { 2gh } $
Question 6 Multiple Choice (Single Answer)

In a collision between two solid spheres. velocity of separation along the line of impact (assume no external forces act on the system of two spheres during impact):

  1. Cannot be greater than velocity of approach
  2. Cannot be less than velocity of approach
  3. Cannot be equal to velocity of approach
  4. none of these
Question 7 Multiple Choice (Single Answer)

Two particles of mass $M _{A} $ and $M _{B} $ and there velocities are $V _{A} $ and $V _{B} $ respectively collides. After collision they inter changes their velocities then ratio of  $\dfrac{M _{A}}{M _{B}}$ is:

  1. (a) $\dfrac{V _{A}}{V _{B}}$
  2. (b) $\dfrac{V _{B}}{V _{A}}$
  3. (c) $\dfrac{V _{A}+V _{B}}{V _{B}-V _{A}}$
  4. (d) 1
Question 8 Multiple Choice (Single Answer)

A plastic ball falls from a height of $4.9$ metre and rebounds several times from the floor. What is the coefficient of restitution during the impact with the floor if $1.3$ seconds pass from the first impact to the second one?

  1. $0.9$
  2. $0.1$
  3. $0.7$
  4. $0.8$
Question 9 Multiple Choice (Single Answer)

A body 'x' with a momentum 'p' collides with with another identical stationary body 'y' dimensionally. During the collision 'y' gives an impulse 'J' to the body 'x'. Then the coefficient of restitution is 

  1. $\dfrac p{p-2J}$
  2. $\dfrac p{p-J}$
  3. $\dfrac p{p+2J}$
  4. $\dfrac p{p+J}$
Question 10 Multiple Choice (Single Answer)

A uniform rod AB of length $L$ and mass $M$ is lying on a smooth table. A small particle of mass $m$ strike the rod with a velocity $v _0$ at point C a distance x from the centre O. The particle comes to rest after collision. The value of $x$, so that point A of the rod remains stationary just after the collision,  is:

  1. $L/3$
  2. $L/6$
  3. $L/4$
  4. $L/12$
Question 11 Multiple Choice (Single Answer)

a body of mass m falls from height h on ground. If e be the coefficient of restitution of collision betwwen the body and ground then the distance travelled by body before it comes to rest is

  1. $h\left\{ {\dfrac{{1\, + {e^2}}}{{1 - {e^2}}}} \right\}$
  2. $h\left\{ {\dfrac{{1\, - {e^2}}}{{1 + {e^2}}}} \right\}$
  3. ${\dfrac{{2eh}}{{1 + {e^2}}}}$
  4. ${\dfrac{{2eh}}{{1 - {e^2}}}}$
Question 12 Multiple Choice (Single Answer)

A solid spherical ball of radius R collides with a rough horizontal surface as shown in figure. At the time of collision its velocity is $v _{0}$ at an angle $\theta$ to the horizontal and angular velocity $\omega _{0}$ as shown. After collision, angular velocity of ball may

  1. decrease
  2. increase
  3. remains constant
  4. none of these
Question 13 Multiple Choice (Single Answer)

If a ball is dropped from rest, it bounces from the floor. The coefficient of restitution is $0.5$ and the speed just before the first bounce is $5\ m/sec$. The total time taken by the ball to come to rest is:

  1. $2\ sec$
  2. $1\ sec$
  3. $0.5\ sec$
  4. $0.25\ sec$
Question 14 Multiple Choice (Multiple Answers)

A solid sphere rolls without slipping on a rough horizontal floor, moving with a speed $v$. It makes an elastic collision with a smooth vertical wall. After impact,

  1. it will move with a speed $v$ initially.
  2. its motion will be rolling without slipping.
  3. its motion will be rolling with slipping initially and its rotational motion will stop momentarily at some instant.
  4. its motion will be rolling without slipping only after some time.
Question 15 Multiple Choice (Single Answer)

An athelete diving off a high spring board can perform a variety of physical moments in the air before entering the water below. Which one of the following parameters will remain constant during the fall? The athelete's:

  1. linear velocity
  2. linear momentum
  3. moment of inertia
  4. angular velocity
Question 16 Multiple Choice (Single Answer)

In an elastic collision, kinetic energy of the relative motion is converted into the ____ energies of two momentarily compressed bodies, and then is converted back into the _____ energy. Fill in the blanks. 

  1. kinetic,kinetic
  2. elastic,kinetic
  3. elastic,elastic
  4. kinetic,elastic
Question 17 Multiple Choice (Single Answer)

State whether the given statement is True or False :

In an elastic collision, the net kinetic energy of the two colliding bodies is conserved.

  1. True
  2. False
Question 18 Multiple Choice (Single Answer)

A ball of mass m moving with a constant velocity u strikes against a ball of same mass at rest. If e is the coefficient of restitution, then what will be the ratio of velocity of two balls after collision?

  1. $\dfrac{1-e}{1+e}$
  2. $\dfrac{e-1}{e+1}$
  3. $\dfrac{1+e}{1-e}$
  4. $\dfrac{e+1}{e-1}$
Question 19 Multiple Choice (Multiple Answers)

A sphere $A$ moving with speed $u$ and rotating with an angular velocity $\omega$ makes a head-on elastic collision with an identical stationary sphere $B$. There is no friction between the surfaces of $A$ and $B$. Choose the correct alternative(s). Discard gravity.

  1. $A$ will stop moving but continue to rotate with an angular velocity $\omega$
  2. $A$ will come to rest and stop rotating
  3. $B$ will move with speed $u$ without rotating
  4. $B$ will move with speed $u$ and rotate with an angular velocity $\omega$.
Question 20 Multiple Choice (Single Answer)

A 20 g ball is fired horizontally toward a 100 g ball that is hanging motionless from a 1.0-m-long string. The balls undergo a head-on, elastic collision, after which the 100 g ball swings out to a maximum angle of 50 degrees. Determine the initial speed of the 20 g ball.

  1. 8.4m/s
  2. 4.2m/s
  3. 2.1m/s
  4. 16.8m/s